Question

A light beam of frequency 5 x 1014 hertz has wavelength 4000Å in a medium of refractive
index u. The value of u is:
a) 1.68
b) 1.60
c) 1.42
d) 1.5​

Answer 1

Answer:

b. 1.60

Explanation:

please follow me

Answer 2

The value of u is: d) 1.5

Given - Frequency and wavelength

Find - Value of u

Solution - Firstly finding the speed of light beam in the medium.

speed = frequency*wavelength

Frequency = 5*10¹⁴ Hz

Wavelength = 4000Å

Wavelength = 4000*10-¹⁰

Wavelength = 4*10-⁷ m

Speed = 5*10¹⁴*4*10-⁷

Speed = 20*10⁷

Speed = 2*10⁸ m/s

Refractive index (u) = speed of light in vaccum/speed of light in medium

Speed of light in vaccum = 3*10⁸ m/s

u = 3*10⁸/2*10⁸

u = 1.5

Hence, the value of u is d) 1.5.

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