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$\bullet$$\bullet$ In a physics lab, light with wavelength 490 nm travels in air from a laser to a photocell in 17.0 ns. When a slab of glass 0.840 m thick is placed in the light beam, with the beam incident along the normal to the parallel faces of the slab, it takes the light 21.2 ns to travel from the laser to the photocell. What is the wavelength of the light in the glass?

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$n=2.50$wavelength$=196 \mathrm{mm}$

Physics 102 Electricity and Magnetism

Physics 103

Chapter 23

Electromagnetic Waves and Propagationof Light

Electromagnetic Waves

Reflection and Refraction of Light

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Lectures

02:30

In optics, ray optics is a geometric optics method that uses ray tracing to model the propagation of light through an optical system. As in all geometric optics methods, the ray optics model assumes that light travels in straight lines and that the index of refraction of the optical material remains constant throughout the system.

10:00

In optics, reflection is the change in direction of a wavefront at an interface between two different media so that the wavefront returns into the medium from which it originated. Common examples include the reflection of light, sound and water waves. The law of reflection says that for specular reflection the angle at which the wave is incident on the surface equals the angle at which it is reflected. Reflection may also be referred to as "mirror image" or "specular reflection". Refraction is the change in direction of a wave due to a change in its speed. The refractive index of a material is a measure of its ability to change the direction of a wave. A material with a higher refractive index will change the direction of a wave to a greater degree than a material with a lower refractive index. When a wave crosses the boundary between two materials with different refractive indices, part of the wave is refracted; that is, it changes direction. The ratio of the speeds of propagation of the two waves determines the angle of refraction, which is the angle between the direction of the incident and the refractive rays.

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$\bullet$$\bullet$ In a ph…

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In a physics lab, light wi…

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Light of wavelength 692 nm…

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A piece of glass with a fl…

02:07

A $750-\mathrm{nm}$ light …

00:32

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07:21

Characteristics of laser l…

03:13

A laser light in air has a…

Let's find the change in transit time with respect to the distance of the slab inserted in the index of refraction of and so we know when the slab is inserted, it moves 0.84 meters, which is the length of the slab over the velocity in this lab. And since velocity is equal to see over in, the velocity in this lab is see over in of the slab. And so this is the time it takes with this live in servant. What's the time it takes without the slab? We'll still going to move that point for meters, but there's just not a slab there. And so the speed is just the speed of light there. This is the change in transit time when the slab was inserted and we know it's equal to 4.2 nanoseconds lies attracting the two times that they give us this equation here, let us sell for in, since everything else is a constant innit? And so this equation sympathize to in minus one times 0.84 over the speed of light equals 4.2 seconds. And we have to keep in mind that this is nanoseconds and so the units are not in the typical sa units. Ultimately, when you sell for in, you'll get 2.5. But just be careful about the Nano seconds here, so this isn't the answer yet, but it's very helpful in determining the answer, because now that we have that, we can find the answer by plying this formula here. Lambda in the material is eagle to Lambda in vacuum over the index of refraction material we're in. And so we know lamb. Tonight it is 490 nana meters that's given in problem, and then we just calculated and it's 2.5, and so this is 196 centimeters, and that's the answer.

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