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Q10.9 Light of wavelength 5000 Å falls on a plane reflecting surface. What are the wavelength and frequency of the reflected light? For what angle of incidence is the reflected ray normal to the incident ray?

Answers (1)

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Given, 

Wavelength of light \lambda =5000\AA =5000*10^{-10}m

Speed of light c=3*10^8

Now,

Wavelength and frequency will be the same when the ray is reflected.

Frequency of reflected light 

f=\frac{c}{\lambda }=\frac{3*10^{8}}{5000*10^{-10}}=6*10^{14}Hz

Hence wavelength and frequency of light is  5000*10^{-10}m and  6*10^{14}Hz respectively.

Now,

as per the law of reflection, angle of incidence i is always equal to angle of reflection r.

i=r

Now, when the reflected ray is perpendicular with incidence ray,

i+r=90

i+i=90

2i=90

i=45

Hence the angle of incidence is 45 for this condition.

Posted by

Pankaj Sanodiya

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