7: A narrow beam of light containing red (660 nm) and blue (470 nm) wavelengths travels from air through a 1.00 cm thick flat piece of crown glass and back to air again. The beam strikes at a 30.0o incident angle. (a) At what angles do the two colours emerge? (b) By what distance are the red and blue separated when they emerge?

Light-App SupportThe F7-120Bi fresnel LED light features a built-in Bluetooth module, which allows it to be controlled via the Godox Light App. This enables you to remotely control the brightness, and colour temperature of a single light or a group of lights independently, or simultaneously from a smartphone or tablet.

Fresnel lights theatre

Impeccable Colour Rendering AbilityWith a CRI rating of 96+ and a TLCI rating of 97+, the F7-120D/Bi faithfully can reproduce colour and skin tones accurately in your scenes. The Godox F7-120Bi fresnel LED light meets the high colour accuracy standards required for film, TV, Broadcasting, and Theatrical Productions.

1: (a) What is the ratio of the speed of red light to violet light in diamond, based on Table 2? (b) What is this ratio in polystyrene? (c) Which is more dispersive?

Adjustable Beam AnglesSince the Godox F7-120Bi features a built-in fresnel LED light lens, you can adjust the beam angle anywhere from 15° to 60°. This allows you to customise the beam angle of the light according to your needs. It also features four-leaf barn doors, enabling you to control the beam angle of light even further.

Fresnellightexample

How does a lens form an image? See how light rays are refracted by a lens. Watch how the image changes when you adjust the focal length of the lens, move the object, move the lens, or move the screen.

On-board ControlsTheGodox F7-120Bi Brightness, colour temperature, beam angle, and DMX address settings can be adjusted through buttons and knobs on the light body.

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FresnelLightprice

5: A parallel beam of light containing orange (610 nm) and violet (410 nm) wavelengths goes from fused quartz to water, striking the surface between them at a 60.0o incident angle. What is the angle between the two colours in water?

The Power of Daisy-ChainingFeaturing AC input and output ports, the Godox F7120Bi fresnel LED light allows you to daisy-chain up to 10 lights in series, reducing the need for messy and complex wiring and making cable management a hassle-free experience.

DMX512 SupportThe Godox F7-120Bi fresnel light supports the industry-standard DMX512 protocol, allowing it to be connected to DMX consoles for multi-light control. This will enable you to control Brightness and colour temperature independently, or simultaneously using the DMX channels.

FresnelLightBulb

Douglas College Physics 1207 Copyright © August 22, 2016 by OpenStax is licensed under a Creative Commons Attribution 4.0 International License, except where otherwise noted.

Refraction is responsible for dispersion in rainbows and many other situations. The angle of refraction depends on the index of refraction, as we saw in Chapter 25.3 The Law of Refraction. We know that the index of refraction n depends on the medium. But for a given medium, n also depends on wavelength. (See Table 2. Note that, for a given medium, n increases as wavelength decreases and is greatest for violet light. Thus violet light is bent more than red light, as shown for a prism in Figure 3(b), and the light is dispersed into the same sequence of wavelengths as seen in Figure 1 and Figure 2.

Fresnellightfunction

We see about six colors in a rainbow—red, orange, yellow, green, blue, and violet; sometimes indigo is listed, too. Those colors are associated with different wavelengths of light, as shown in Figure 2. When our eye receives pure-wavelength light, we tend to see only one of the six colors, depending on wavelength. The thousands of other hues we can sense in other situations are our eye’s response to various mixtures of wavelengths. White light, in particular, is a fairly uniform mixture of all visible wavelengths. Sunlight, considered to be white, actually appears to be a bit yellow because of its mixture of wavelengths, but it does contain all visible wavelengths. The sequence of colors in rainbows is the same sequence as the colors plotted versus wavelength in Figure 2. What this implies is that white light is spread out according to wavelength in a rainbow. Dispersion is defined as the spreading of white light into its full spectrum of wavelengths. More technically, dispersion occurs whenever there is a process that changes the direction of light in a manner that depends on wavelength. Dispersion, as a general phenomenon, can occur for any type of wave and always involves wavelength-dependent processes.

Any type of wave can exhibit dispersion. Sound waves, all types of electromagnetic waves, and water waves can be dispersed according to wavelength. Dispersion occurs whenever the speed of propagation depends on wavelength, thus separating and spreading out various wavelengths. Dispersion may require special circumstances and can result in spectacular displays such as in the production of a rainbow. This is also true for sound, since all frequencies ordinarily travel at the same speed. If you listen to sound through a long tube, such as a vacuum cleaner hose, you can easily hear it is dispersed by interaction with the tube. Dispersion, in fact, can reveal a great deal about what the wave has encountered that disperses its wavelengths. The dispersion of electromagnetic radiation from outer space, for example, has revealed much about what exists between the stars—the so-called empty space.

Bright and Even LightingWith its powerful COB LED chip, combined with a high-quality 7” Fresnel lens, the F7-120bi fresnel LED light produces an even, uniform spotlight effect with a feathered edge. Due to the way that Fresnel lenses have been designed, it reduces effectively power loss over distance, allowing them to achieve a brightness of up to 71,100 lux at 1 meter.

4: (a) A narrow beam of light containing yellow (580 nm) and green (550 nm) wavelengths goes from polystyrene to air, striking the surface at a 30.0o incident angle. What is the angle between the colours when they emerge? (b) How far would they have to travel to be separated by 1.00 mm?

Silent, Efficient CoolingFeaturing a fanless, all-metal body with multiple heat dissipation slits, the Godox F7-120Bi it quiet and efficient cooling. This ensures you can shoot for prolonged periods, without having to worry about overheating issues. This also results in a longer lifespan for the F7-120Bi fixture itself.

FresnellightLED

Rainbows are produced by a combination of refraction and reflection. You may have noticed that you see a rainbow only when you look away from the sun. Light enters a drop of water and is reflected from the back of the drop, as shown in Figure 4. The light is refracted both as it enters and as it leaves the drop. Since the index of refraction of water varies with wavelength, the light is dispersed, and a rainbow is observed, as shown in Figure 5 (a). (There is no dispersion caused by reflection at the back surface, since the law of reflection does not depend on wavelength.) The actual rainbow of colors seen by an observer depends on the myriad of rays being refracted and reflected toward the observer’s eyes from numerous drops of water. The effect is most spectacular when the background is dark, as in stormy weather, but can also be observed in waterfalls and lawn sprinklers. The arc of a rainbow comes from the need to be looking at a specific angle relative to the direction of the sun, as illustrated in Figure 5 (b). (If there are two reflections of light within the water drop, another “secondary” rainbow is produced. This rare event produces an arc that lies above the primary rainbow arc—see Figure 5 (c).)

Everyone enjoys the spectacle of a rainbow glimmering against a dark stormy sky. How does sunlight falling on clear drops of rain get broken into the rainbow of colors we see? The same process causes white light to be broken into colors by a clear glass prism or a diamond. (See Figure 1.)

Variable Colour-TemperaturesThe Godox F7-120Bi features variable colour temperatures, ranging from 3200K to 5600K, allowing you to either match the colour temperature of the ambient lighting in your shooting environment or to add mood and ambience to your scenes; Warmer colour temperatures produce a more relaxed and inviting atmosphere, whereas the cooler colour temperatures are great for establishing professional and more serious settings. This makes the F7-120Bi fresnel LED light great for all filming situations.

8: A narrow beam of white light enters a prism made of crown glass at a 45.0o incident angle, as shown below in Figure 7. At what angles, θRed and θViolet do the red (660 nm) and violet (410 nm) components of the light emerge from the prism?

Fresnellightpronunciation

Fresnellighteffect

Dispersion may produce beautiful rainbows, but it can cause problems in optical systems. White light used to transmit messages in a fiber is dispersed, spreading out in time and eventually overlapping with other messages. Since a laser produces a nearly pure wavelength, its light experiences little dispersion, an advantage over white light for transmission of information. In contrast, dispersion of electromagnetic waves coming to us from outer space can be used to determine the amount of matter they pass through. As with many phenomena, dispersion can be useful or a nuisance, depending on the situation and our human goals.

2: A beam of white light goes from air into water at an incident angle of 75.0 degrees. At what angles are the red (660 nm) and violet (410 nm) parts of the light refracted?

The Godox F7-120Bi is a Bi-Colour Fresnel LED Light with high colour rendering ratings at a CRI of 96+, and a TLCI of 97+, variable colour temperatures between 3200 and 5600K, and flicker-free lighting. Featuring a Built-in 7” Fresnel Lens, the beam angle is adjustable anywhere between 15 to 60 degrees. The Godox F7-120Bi supports Bluetooth enabling it to be controlled via the Godox Light App, as well as support for the industry standard DMX512 control protocol, for larger productions. It is suitable for adding rim lighting to your subjects or creating a spotlight effect in settings such as small television studios, virtual studios, stage studios, campus TV stations, and more.

6: A ray of 610 nm light goes from air into fused quartz at an incident angle of 55.0o. At what incident angle must 470 nm light enter flint glass to have the same angle of refraction?