Question

The wavelength of light in air is 6000 A.U. Find the number of waves in path length of 10 cm in glass of

refractive index 1.5.​

Answer 1

Answer:

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Explanation: In air velocity of light is 3×10  

8

m/s and wavelength is 6000A  

o

=6000×10  

−10

m

We know that c=λ×f , f=frequency

3×10  

8

=6000×10  

−10

×f

f=5×10  

14

Hz

We know that refractive index n=  

velocityoflightinmedium

velocityoflightinvacuum

​  

=  

v

c

​  

 

Here c=3×10  

8

m/s

So 1.5=  

v

3×10  

8

 

​  

 

⟹v=2×10  

8

m/s

Since frequency does not change when light enters from one medium to other.  

v=λf

2×10  

8

=λ×5×10  

14

 

λ=4×10  

−7

m=4000A  

​