A laser beam with vacuum wavelength 632.8 nm is incident from air onto a block o

Question

A laser beam with vacuum wavelength 632.8 nm is incident from air onto a block of Lucite as shown in the figure below. The line of sight of the photograph is perpendicular to the plane in which the light moves. (Assume that the incidence angle is 65

A laser beam with vacuum wavelength 632.8 nm is incident from air onto a block of Lucite as shown in the figure below. The line of sight of the photograph is perpendicular to the plane in which the light moves. (Assume that the incidence angle is 65 degree, and the refraction angle is 36 degree.) (a) Find the speed of the light in the Lucite. m/s (b) Find the frequency of the light in the Lucite. Hz (c) Find the wavelength of the light in the Lucite. nm

Explanation / Answer

Here ,

angle of incidence , i = 65 degree

angle of refraction , r = 36 degree

Now, let the refractive index of lucite is n

using snell's law

n*sin(r) = 1*sin(i)

n*sin(36) = 1*sin(65)

n = 1.542

speed of light = 3*10^8/1.542

speed of light = 1.946 *10^8 m/s

b)

as frequency of light stays the same in all mediums

speed = frequency * wavelength

3 *10^8 = frequency * 632.8 *10^-9

frequency = 4.741 *10^14 Hz

c)

in the lucite ,

wavelength in lucite = 632.8/1.542

wavelength in lucite =410.4 nm

the wavelength in lucite is 410.4 nm

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