Lightmicroscope

How does a lens form images?. We can build up a lens from a series of prisms We could add a 2nd. prism, to deviate light more, so that two rays go through the same place There are a variety of lens, but essentially they are converging (usually convex) diverging (usually concave) Convex lenses create a real image (i.e. one that can be cast on a screen) The most important quantity for a lens is the focal length f: i.e. how far from the lens do parallel rays get focussed. Concave lenses cause light to diverge, but the rays can be traced back to an (imaginary) focus. Images are formed as either real or virtual: only a convex lens (positive focal length) can form a real image Rules for "ray-tracing" diagrams: a ray which goes through the centre of the lens is not deflected. a ray that is parallel to the axis must go through the focus. a ray that goes through a focus must go parallel to the axis. We can simulate lens on an optical bench The Thin Lens Formula This is the derivation of the "thin-lens" formula. We can use this to find the relation between the distance to the object, the image and the focal length The magnification \color{red}{ M = \frac{{{\rm{image height}}}}{{{\rm{object height}}}} = \frac{{h_i }}{{h_0 }}} (M can be < 1) We have two sets of similar triangles: \color{red}{ \left| {\frac{{h_i }}{{h_0 }}} \right| = \frac{{d_i }}{{d_0 }} = \frac{{d_i - f}}{f}} so \color{red}{ \frac{{d_i - f}}{f} = \frac{{d_i }}{{d_0 }} \Rightarrow \frac{1}{f} = \frac{1}{{d_0 }} + \frac{1}{{d_i }}} The thin lens equation \color{red}{ \frac{1}{f} = \frac{1}{{d_0 }} + \frac{1}{{d_i }}} In words 1 = 1 + 1 focal length object dist. image dist. The surprising thing about this formula is that it always works provided we remember certain conventions: real objects have do > 0 real images have di> 0 virtual ones have di < 0 objects above the axis have ho > 0 images below the axis have hi < 0 convex lenses have f > 0 concave lenses have f <0 convex mirrors have f < 0 concave mirrors have f >0 mirrors have real images on the same side as the object lenses must be "thin": the approx. that is used is sin(θ)= θ e.g suppose we have a lens with f = 20 cm and an 3 cm high object is placed at a distance of 35 cm: where is the image, and how big is it? We can simulate lens on an optical bench The lens-maker's equation: \color{red}{ \frac{1}{f} = \left( {n - 1} \right)\left( {\frac{1}{{R_1 }} + \frac{1}{{R_2 }}} \right)} applies if the lens is "thin" (means that all angles are small enough so that θ = sin(θ)) R₁,R₂ are the radii of curvature of the lens surface: convex surfaces have positive curvature, e.g. suppose R₁ = 10, R₂ = 20, n = 1.4: what is f? 16.6 cm 30.0 cm 12 cm 0.060cm Focal length of a mirror: f = R/2 because if you place a source at the centre the light must be reflected back there. 1 = 1 + 1 f R R We can simulate a mirror on an optical bench e.g. a spoon What happens if you look at the front of the spoon? What is the focal length? What happens if you put an object inside the focal length? What happens if you look at the front of the spoon? Image is real and inverted What happens if you put an object inside the focal length? Image is virtual and upright. Note we are drawing dotted lines to extend the rays through the foci. The back of a spoon acts as a convex mirror. The radius of curvature is 10 cm. The focal length is -20 cm? 10 cm? 5 cm? -5 cm? The back of a spoon acts as a convex mirror. The radius of curvature is 10 cm. The focal length is -5 cm. The image of your face will be real and inverted orientation real and same orientation virtual and inverted orientation virtual and same orientation Before we can look at more complicated systems of lenses, we need to understand the effects of light as a wave: this is "physical optics"

-20 cm? 10 cm? 5 cm? -5 cm? The back of a spoon acts as a convex mirror. The radius of curvature is 10 cm. The focal length is -5 cm. The image of your face will be real and inverted orientation real and same orientation virtual and inverted orientation virtual and same orientation Before we can look at more complicated systems of lenses, we need to understand the effects of light as a wave: this is "physical optics"

Parfocal, The specimen is focused for all objectives if it is focused for one objective. In other words, once the specimen is focused under one objective it will be in approximate focus under other objectives.

What is the function ofpillar inmicroscope

T Back to top Tube, the tube houses many of the optical components of the microscope. The optical tube length of most biomedical microscopes is 160 millimeters but tube geometry varies considerably due to relay lenses and proprietary design features. In most modern microscopes the tube is folded to make the microscope easier to use.   Early microscopes had straight tubes such as this model built by Robert Hooke in the mid 17th century. Tube length, describes the optical tube length for which the objective was designed. This is 160 mm (6.3 inches) for modern biomedical microscopes.   Turret, Most microscopes have several objective lenses mounted on a rotating turret to facilitate changing lenses. An audible click identifies the correct position for each lens as it swings into place. When the turret is rotated, it should be grasped by the ring around its edge, and not by the objectives. Using the objectives as handles can de-center and possibly damage them.

S Back to top Stage, The stage is the platform that supports the specimen. It is usually quite large to minimize vibration and it attaches to the microscope stand. The stage has an opening for the illuminating beam of light to pass through.   A spring loaded clip holds the specimen slide in place on the stage. Other types of stage clips are designed for use with petri-dishes, multiwell plates, or other specialized chambers.   Most stages have a rack and pinion mechanism that can move the specimen slide in two perpendicular (X - Y) directions. On many microscopes, stage movement is controlled using two concentric knobs located to the side or below the stage.   Stand, The stand is the basic structure of the microscope to which everything is attached. The stand, also known as the arm, is the part of the microscope that you grab to transport the microscope.

What is the function ofbrightness adjustment inmicroscope

Light can go from a dense medium to a less dense one at an "impossible" angle: e.g in crown glass, what would happen to a ray whose angle of incidence was θ = 60o? e.g. lying on the bottom of a swimming pool looking up what do you see? A prism can be used to show total internal reflection In crown glass, what would the angle of incidence need to be such that the outgoing ray was exactly at 900? 60o 90o 42o 48o Total Internal reflection can occur repeatedly: this is the idea behind fibre optics. If you want to carry a large amount of signal on one carrier, need a very high frequency (roughly, a voice channel needs 10 kHz, so to carry N voice channels, need 10N kHz. How many voice channels can you carry on a 1 MHz radio wave? How many could you carry on red light? Lenses How does a lens form images?. We can build up a lens from a series of prisms We could add a 2nd. prism, to deviate light more, so that two rays go through the same place There are a variety of lens, but essentially they are converging (usually convex) diverging (usually concave) Convex lenses create a real image (i.e. one that can be cast on a screen) The most important quantity for a lens is the focal length f: i.e. how far from the lens do parallel rays get focussed. Concave lenses cause light to diverge, but the rays can be traced back to an (imaginary) focus. Images are formed as either real or virtual: only a convex lens (positive focal length) can form a real image Rules for "ray-tracing" diagrams: a ray which goes through the centre of the lens is not deflected. a ray that is parallel to the axis must go through the focus. a ray that goes through a focus must go parallel to the axis. We can simulate lens on an optical bench The Thin Lens Formula This is the derivation of the "thin-lens" formula. We can use this to find the relation between the distance to the object, the image and the focal length The magnification \color{red}{ M = \frac{{{\rm{image height}}}}{{{\rm{object height}}}} = \frac{{h_i }}{{h_0 }}} (M can be < 1) We have two sets of similar triangles: \color{red}{ \left| {\frac{{h_i }}{{h_0 }}} \right| = \frac{{d_i }}{{d_0 }} = \frac{{d_i - f}}{f}} so \color{red}{ \frac{{d_i - f}}{f} = \frac{{d_i }}{{d_0 }} \Rightarrow \frac{1}{f} = \frac{1}{{d_0 }} + \frac{1}{{d_i }}} The thin lens equation \color{red}{ \frac{1}{f} = \frac{1}{{d_0 }} + \frac{1}{{d_i }}} In words 1 = 1 + 1 focal length object dist. image dist. The surprising thing about this formula is that it always works provided we remember certain conventions: real objects have do > 0 real images have di> 0 virtual ones have di < 0 objects above the axis have ho > 0 images below the axis have hi < 0 convex lenses have f > 0 concave lenses have f <0 convex mirrors have f < 0 concave mirrors have f >0 mirrors have real images on the same side as the object lenses must be "thin": the approx. that is used is sin(θ)= θ e.g suppose we have a lens with f = 20 cm and an 3 cm high object is placed at a distance of 35 cm: where is the image, and how big is it? We can simulate lens on an optical bench The lens-maker's equation: \color{red}{ \frac{1}{f} = \left( {n - 1} \right)\left( {\frac{1}{{R_1 }} + \frac{1}{{R_2 }}} \right)} applies if the lens is "thin" (means that all angles are small enough so that θ = sin(θ)) R₁,R₂ are the radii of curvature of the lens surface: convex surfaces have positive curvature, e.g. suppose R₁ = 10, R₂ = 20, n = 1.4: what is f? 16.6 cm 30.0 cm 12 cm 0.060cm Focal length of a mirror: f = R/2 because if you place a source at the centre the light must be reflected back there. 1 = 1 + 1 f R R We can simulate a mirror on an optical bench e.g. a spoon What happens if you look at the front of the spoon? What is the focal length? What happens if you put an object inside the focal length? What happens if you look at the front of the spoon? Image is real and inverted What happens if you put an object inside the focal length? Image is virtual and upright. Note we are drawing dotted lines to extend the rays through the foci. The back of a spoon acts as a convex mirror. The radius of curvature is 10 cm. The focal length is -20 cm? 10 cm? 5 cm? -5 cm? The back of a spoon acts as a convex mirror. The radius of curvature is 10 cm. The focal length is -5 cm. The image of your face will be real and inverted orientation real and same orientation virtual and inverted orientation virtual and same orientation Before we can look at more complicated systems of lenses, we need to understand the effects of light as a wave: this is "physical optics"

B Back to top Base, The base is the foundation on which the microscope stand is built. It is important that the base is relatively large, stable, and massive. When you are setting up a microscope for the first time ensure that the surface on which it is placed is level.

I Back to top Illuminator, There is an illuminator built into the base of most microscopes. The purpose of the illuminator is to provide even, high intensity light at the place of the field aperture, so that light can travel through the condensor to the specimen.

What is the function ofstage clip inmicroscope

A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z

P Back to top   Plan, There are many different kinds of objective lenses. Common designations include "plan" for flat field, "achromat" for partially color-corrected, and "apochromat" for highly color corrected. These designations may become combined as in "plan achromat."

What is the Function ofilluminator inmicroscope

What is the refracted angle? 59.40 52.50 23.30 22.50 We have already seen how a single surface refracts. All optical instruments have at least 2 surfaces. A prism deflects light via two successive refractions sin(θ₁) = n sin(θ₂) etc Total Internal Reflection Light can go from a dense medium to a less dense one at an "impossible" angle: e.g in crown glass, what would happen to a ray whose angle of incidence was θ = 60o? e.g. lying on the bottom of a swimming pool looking up what do you see? A prism can be used to show total internal reflection In crown glass, what would the angle of incidence need to be such that the outgoing ray was exactly at 900? 60o 90o 42o 48o Total Internal reflection can occur repeatedly: this is the idea behind fibre optics. If you want to carry a large amount of signal on one carrier, need a very high frequency (roughly, a voice channel needs 10 kHz, so to carry N voice channels, need 10N kHz. How many voice channels can you carry on a 1 MHz radio wave? How many could you carry on red light? Lenses How does a lens form images?. We can build up a lens from a series of prisms We could add a 2nd. prism, to deviate light more, so that two rays go through the same place There are a variety of lens, but essentially they are converging (usually convex) diverging (usually concave) Convex lenses create a real image (i.e. one that can be cast on a screen) The most important quantity for a lens is the focal length f: i.e. how far from the lens do parallel rays get focussed. Concave lenses cause light to diverge, but the rays can be traced back to an (imaginary) focus. Images are formed as either real or virtual: only a convex lens (positive focal length) can form a real image Rules for "ray-tracing" diagrams: a ray which goes through the centre of the lens is not deflected. a ray that is parallel to the axis must go through the focus. a ray that goes through a focus must go parallel to the axis. We can simulate lens on an optical bench The Thin Lens Formula This is the derivation of the "thin-lens" formula. We can use this to find the relation between the distance to the object, the image and the focal length The magnification \color{red}{ M = \frac{{{\rm{image height}}}}{{{\rm{object height}}}} = \frac{{h_i }}{{h_0 }}} (M can be < 1) We have two sets of similar triangles: \color{red}{ \left| {\frac{{h_i }}{{h_0 }}} \right| = \frac{{d_i }}{{d_0 }} = \frac{{d_i - f}}{f}} so \color{red}{ \frac{{d_i - f}}{f} = \frac{{d_i }}{{d_0 }} \Rightarrow \frac{1}{f} = \frac{1}{{d_0 }} + \frac{1}{{d_i }}} The thin lens equation \color{red}{ \frac{1}{f} = \frac{1}{{d_0 }} + \frac{1}{{d_i }}} In words 1 = 1 + 1 focal length object dist. image dist. The surprising thing about this formula is that it always works provided we remember certain conventions: real objects have do > 0 real images have di> 0 virtual ones have di < 0 objects above the axis have ho > 0 images below the axis have hi < 0 convex lenses have f > 0 concave lenses have f <0 convex mirrors have f < 0 concave mirrors have f >0 mirrors have real images on the same side as the object lenses must be "thin": the approx. that is used is sin(θ)= θ e.g suppose we have a lens with f = 20 cm and an 3 cm high object is placed at a distance of 35 cm: where is the image, and how big is it? We can simulate lens on an optical bench The lens-maker's equation: \color{red}{ \frac{1}{f} = \left( {n - 1} \right)\left( {\frac{1}{{R_1 }} + \frac{1}{{R_2 }}} \right)} applies if the lens is "thin" (means that all angles are small enough so that θ = sin(θ)) R₁,R₂ are the radii of curvature of the lens surface: convex surfaces have positive curvature, e.g. suppose R₁ = 10, R₂ = 20, n = 1.4: what is f? 16.6 cm 30.0 cm 12 cm 0.060cm Focal length of a mirror: f = R/2 because if you place a source at the centre the light must be reflected back there. 1 = 1 + 1 f R R We can simulate a mirror on an optical bench e.g. a spoon What happens if you look at the front of the spoon? What is the focal length? What happens if you put an object inside the focal length? What happens if you look at the front of the spoon? Image is real and inverted What happens if you put an object inside the focal length? Image is virtual and upright. Note we are drawing dotted lines to extend the rays through the foci. The back of a spoon acts as a convex mirror. The radius of curvature is 10 cm. The focal length is -20 cm? 10 cm? 5 cm? -5 cm? The back of a spoon acts as a convex mirror. The radius of curvature is 10 cm. The focal length is -5 cm. The image of your face will be real and inverted orientation real and same orientation virtual and inverted orientation virtual and same orientation Before we can look at more complicated systems of lenses, we need to understand the effects of light as a wave: this is "physical optics"

What is the function ofstage inmicroscope

C Back to top Condenser, The condenser under the stage focuses the light on the specimen, adjusts the amount of light on the specimen, and shapes the cone of light entering the objective. One way to think about the condenser is as a light "pump" that concentrates light onto the specimen.

The condenser has an iris diaphragm that controls the angle of the beam of light focused onto the specimen. The iris diaphram is an adjustable shutter which allows you to adjust the amount of light passing through the condenser. The angle determines the Numerical Aperture (NA) of the condenser. This diaphragm, generally called the aperture diaphragm, is one of the most important controls on the microscope.   Cover slip, Most objectives are designed for use with a cover slip between the objective and the specimen. The cover slip becomes part of the optical system, and its thickness is critical for optimal perfomance of the objective. The cover slip thickness designation on most objective lenses is 0.17 mm or 170 microns.

When the turret is rotated, it should be grasped by the ring around its edge, and not by the objectives. Using the objectives as handles can de-center and possibly damage them.

O Back to top Objective Lens, The objective lens is the single most important component of the microscope. Together with the condenser, it determines the resolution that the microscope's capability. Learning how to use the correct objective for a particular application is a prerequisite for good microscopy.   Important information describing the objective lens is engraved on the side of its barrel. This is the best performance the objective is capable of and it will only yield this performance when used properly. Ocular Lenses, The ocular lenses are the lens closest to the eye and usually have a 10x magnification. Since light microscopes use binocular lenses there is a lens for each eye. It is important to adjust the distance between the microscope oculars, so that it matches your interpupillary distance. This will yield better image quality and reduce eye strain.

N Back to top Numerical Aperture (NA), The maximum angle from which it can accept light. Lenses that accept light from higher angles have greater resolving power, thus NA defines resolving power. The maximum NA of objectives is 1.4, and it is limited by the physics of light and the refractive index of glass.

What is the function of base

M Back to top Magnification, The degree to which the image of the specimen is enlarged by the objective. For example, 40 specifies 40 times (40x) the actual size of the specimen. As magnification increases, resolution (NA) must also increase so that more information can be obtained. Magnification without increased resolution yields no additional information and is called "empty magnification."

F Back to top Focus (coarse), The coarse focus knob is used to bring the specimen into approximate or near focus.   Focus (fine), Use the fine focus knob to sharpen the focus quality of the image after it has been brought into focus with the coarse focus knob.

Microscope Anatomy & Function Glossary Back to Quicktime VR Microscope   A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z   A Back to top   B Back to top Base, The base is the foundation on which the microscope stand is built. It is important that the base is relatively large, stable, and massive. When you are setting up a microscope for the first time ensure that the surface on which it is placed is level.     C Back to top Condenser, The condenser under the stage focuses the light on the specimen, adjusts the amount of light on the specimen, and shapes the cone of light entering the objective. One way to think about the condenser is as a light "pump" that concentrates light onto the specimen.   The condenser has an iris diaphragm that controls the angle of the beam of light focused onto the specimen. The iris diaphram is an adjustable shutter which allows you to adjust the amount of light passing through the condenser. The angle determines the Numerical Aperture (NA) of the condenser. This diaphragm, generally called the aperture diaphragm, is one of the most important controls on the microscope.   Cover slip, Most objectives are designed for use with a cover slip between the objective and the specimen. The cover slip becomes part of the optical system, and its thickness is critical for optimal perfomance of the objective. The cover slip thickness designation on most objective lenses is 0.17 mm or 170 microns. D Back to top   E Back to top   F Back to top Focus (coarse), The coarse focus knob is used to bring the specimen into approximate or near focus.   Focus (fine), Use the fine focus knob to sharpen the focus quality of the image after it has been brought into focus with the coarse focus knob.   G Back to top   H Back to top   I Back to top Illuminator, There is an illuminator built into the base of most microscopes. The purpose of the illuminator is to provide even, high intensity light at the place of the field aperture, so that light can travel through the condensor to the specimen.   J Back to top   K Back to top   L Back to top   M Back to top Magnification, The degree to which the image of the specimen is enlarged by the objective. For example, 40 specifies 40 times (40x) the actual size of the specimen. As magnification increases, resolution (NA) must also increase so that more information can be obtained. Magnification without increased resolution yields no additional information and is called "empty magnification."   N Back to top Numerical Aperture (NA), The maximum angle from which it can accept light. Lenses that accept light from higher angles have greater resolving power, thus NA defines resolving power. The maximum NA of objectives is 1.4, and it is limited by the physics of light and the refractive index of glass.   O Back to top Objective Lens, The objective lens is the single most important component of the microscope. Together with the condenser, it determines the resolution that the microscope's capability. Learning how to use the correct objective for a particular application is a prerequisite for good microscopy.   Important information describing the objective lens is engraved on the side of its barrel. This is the best performance the objective is capable of and it will only yield this performance when used properly. Ocular Lenses, The ocular lenses are the lens closest to the eye and usually have a 10x magnification. Since light microscopes use binocular lenses there is a lens for each eye. It is important to adjust the distance between the microscope oculars, so that it matches your interpupillary distance. This will yield better image quality and reduce eye strain.   P Back to top   Plan, There are many different kinds of objective lenses. Common designations include "plan" for flat field, "achromat" for partially color-corrected, and "apochromat" for highly color corrected. These designations may become combined as in "plan achromat." Parfocal, The specimen is focused for all objectives if it is focused for one objective. In other words, once the specimen is focused under one objective it will be in approximate focus under other objectives. Q Back to top   R Back to top   S Back to top Stage, The stage is the platform that supports the specimen. It is usually quite large to minimize vibration and it attaches to the microscope stand. The stage has an opening for the illuminating beam of light to pass through.   A spring loaded clip holds the specimen slide in place on the stage. Other types of stage clips are designed for use with petri-dishes, multiwell plates, or other specialized chambers.   Most stages have a rack and pinion mechanism that can move the specimen slide in two perpendicular (X - Y) directions. On many microscopes, stage movement is controlled using two concentric knobs located to the side or below the stage.   Stand, The stand is the basic structure of the microscope to which everything is attached. The stand, also known as the arm, is the part of the microscope that you grab to transport the microscope.   T Back to top Tube, the tube houses many of the optical components of the microscope. The optical tube length of most biomedical microscopes is 160 millimeters but tube geometry varies considerably due to relay lenses and proprietary design features. In most modern microscopes the tube is folded to make the microscope easier to use.   Early microscopes had straight tubes such as this model built by Robert Hooke in the mid 17th century. Tube length, describes the optical tube length for which the objective was designed. This is 160 mm (6.3 inches) for modern biomedical microscopes.   Turret, Most microscopes have several objective lenses mounted on a rotating turret to facilitate changing lenses. An audible click identifies the correct position for each lens as it swings into place. When the turret is rotated, it should be grasped by the ring around its edge, and not by the objectives. Using the objectives as handles can de-center and possibly damage them. U Back to top   V Back to top   W Back to top   X Back to top   Y Back to top   Z Back to top   Back to Quicktime VR Microscope

Microscope

How does a lens form images?. We can build up a lens from a series of prisms We could add a 2nd. prism, to deviate light more, so that two rays go through the same place There are a variety of lens, but essentially they are converging (usually convex) diverging (usually concave) Convex lenses create a real image (i.e. one that can be cast on a screen) The most important quantity for a lens is the focal length f: i.e. how far from the lens do parallel rays get focussed. Concave lenses cause light to diverge, but the rays can be traced back to an (imaginary) focus. Images are formed as either real or virtual: only a convex lens (positive focal length) can form a real image Rules for "ray-tracing" diagrams: a ray which goes through the centre of the lens is not deflected. a ray that is parallel to the axis must go through the focus. a ray that goes through a focus must go parallel to the axis. We can simulate lens on an optical bench The Thin Lens Formula This is the derivation of the "thin-lens" formula. We can use this to find the relation between the distance to the object, the image and the focal length The magnification \color{red}{ M = \frac{{{\rm{image height}}}}{{{\rm{object height}}}} = \frac{{h_i }}{{h_0 }}} (M can be < 1) We have two sets of similar triangles: \color{red}{ \left| {\frac{{h_i }}{{h_0 }}} \right| = \frac{{d_i }}{{d_0 }} = \frac{{d_i - f}}{f}} so \color{red}{ \frac{{d_i - f}}{f} = \frac{{d_i }}{{d_0 }} \Rightarrow \frac{1}{f} = \frac{1}{{d_0 }} + \frac{1}{{d_i }}} The thin lens equation \color{red}{ \frac{1}{f} = \frac{1}{{d_0 }} + \frac{1}{{d_i }}} In words 1 = 1 + 1 focal length object dist. image dist. The surprising thing about this formula is that it always works provided we remember certain conventions: real objects have do > 0 real images have di> 0 virtual ones have di < 0 objects above the axis have ho > 0 images below the axis have hi < 0 convex lenses have f > 0 concave lenses have f <0 convex mirrors have f < 0 concave mirrors have f >0 mirrors have real images on the same side as the object lenses must be "thin": the approx. that is used is sin(θ)= θ e.g suppose we have a lens with f = 20 cm and an 3 cm high object is placed at a distance of 35 cm: where is the image, and how big is it? We can simulate lens on an optical bench The lens-maker's equation: \color{red}{ \frac{1}{f} = \left( {n - 1} \right)\left( {\frac{1}{{R_1 }} + \frac{1}{{R_2 }}} \right)} applies if the lens is "thin" (means that all angles are small enough so that θ = sin(θ)) R₁,R₂ are the radii of curvature of the lens surface: convex surfaces have positive curvature, e.g. suppose R₁ = 10, R₂ = 20, n = 1.4: what is f? 16.6 cm 30.0 cm 12 cm 0.060cm Focal length of a mirror: f = R/2 because if you place a source at the centre the light must be reflected back there. 1 = 1 + 1 f R R We can simulate a mirror on an optical bench e.g. a spoon What happens if you look at the front of the spoon? What is the focal length? What happens if you put an object inside the focal length? What happens if you look at the front of the spoon? Image is real and inverted What happens if you put an object inside the focal length? Image is virtual and upright. Note we are drawing dotted lines to extend the rays through the foci. The back of a spoon acts as a convex mirror. The radius of curvature is 10 cm. The focal length is -20 cm? 10 cm? 5 cm? -5 cm? The back of a spoon acts as a convex mirror. The radius of curvature is 10 cm. The focal length is -5 cm. The image of your face will be real and inverted orientation real and same orientation virtual and inverted orientation virtual and same orientation Before we can look at more complicated systems of lenses, we need to understand the effects of light as a wave: this is "physical optics"

Objectives: by the end of this you will be able to explain mirrors understand Snell's law and refraction find what happens to light when it hits a transparent medium Draw ray diagrams Make calculations with simple lenses

What happens if you look at the front of the spoon? What is the focal length? What happens if you put an object inside the focal length?