## More Questions on This Topic :

Question 1. On a glass plate a light wave is incident at an angle of 60. If the reflected and the refracted waves are mutually perpendicular, the refractive index of material is
1.    √32
2.    √3
3.    32
4.    1√3
: B

from figure Angle of refraction =r
Angle of incidence is equal to angle of reflection [law of reflection]
Angle of reflection =60
Given that reflected and refracted ray are perpendicular.
From figure
60+90+r=180 [angle sum property]
r=30
i=60,r=30
so μ=sin60sin30=3

Question 2. The refractive index of a piece of transparent quartz is the greatest for

[MP PET 1985, 94]
1.    Red light
2.    Violet light
3.    Green light
4.    Yellow light
: B Question 3. The ratio of the refractive index of red light to blue light in air is

[CPMT 1978]
1.    Less than unity
2.    Equal to unity
3.    Greater than unity
4.    Less as well as greater than unity depending upon the experimental arrangement
: A Question 4. Monochromatic light is refracted from air into the glass of refractive index The ratio of the wavelength of incident and refracted waves is

[JIPMER 2000; MP PMT 1996, 2003]
: C Question 5. A ray of light passes from vacuum into a medium of refractive index μ,the angle of incidence is found to be twice the angle of refraction. Then the angle of incidence is
1.    cos−1(μ2)
2.    2cos−1(μ2)
3.    2sin−1(μ)
4.    2sin−1(μ2)
: B

By using μ=sinisinrμ=sin2rsinr=2sinrcosrsinr
r=cos1(μ2).So,i=2r=2cos1(μ2)

Question 6. The refractive index of a certain glass is 1.5 for light whose wavelength in vacuum is 6000 Å. The wavelength of this light when it passes through glass is

[NCERT 1979; CBSE PMT 1993; MP PET 1985, 89]
1.    4000 Å
2.    6000 Å
3.    9000 Å
4.    15000 Å 