UNIT VII: Wave Optics - Online Test
Q1. A plane glass is placed over a various coloured letters (violet, green, yellow, red) The letter which appears to be raised more is,
Answer : Option D
Explaination / Solution:
The refractive index (n) of the glass is different for different colours. For violet n is high.
∴ Violet travel with low speed, so deviation is high.
Q2. Two point white dots are 1 mm apart on a black paper. They are viewed by eye of pupil diameter 3 mm approximately. The maximum distance at which these dots can be resolved by the eye is, [take wavelength of light, λ = 500 nm]
Answer : Option B
Explaination / Solution:
Resolution
limit = 1.22 × λ / D
D
- diameter of pupil = 3 mm
λ
- wavelength = 500 nm
Resolution limit = distance between the dots / resolving diameter
=
1mm/d
[
1.22 × λ ] / D = 1mm / d
D
= [1mm × D ] / [ 1.22 × λ ] = [ 1
x 10-3 × 3 x 10-3 ] / [ 1.22 × 500 x10-9 ]
d = 4.918 ≈ 5m
Q3. In a Young’s double-slit experiment, the slit separation is doubled. To maintain the same fringe spacing on the screen, the screen-to-slit distance D must be changed to,
Answer : Option A
Explaination / Solution:
Q4. Two coherent monochromatic light beams of intensities I and 4I are superposed. The maximum and minimum possible intensities in the resulting beam are
Answer : Option C
Explaination / Solution:
Imax
= I1 + I2 + 2√(I1I2)
=
I + 4I + 2√(4I2)
=
I + 4I + 4I = 9I
Imin
= I1 + I2 - 2√(I1I2)
=
I + 4I − 2√(4I2)
=
I + 4I − 4I = I
Q5. When
light is incident on a soap film of thickness 5×10–5 cm, the
wavelength of light reflected maximum in the visible region is 5320 Å.
Refractive index of the film will be,
Answer : Option B
Explaination / Solution:
d
= 5 × 10-5
cm = 5 × 10-7
m
λ=5320
Å = 5.32 × 10-7 m
For
visible region n=2
μ=?
Q6. First
diffraction minimum due to a single slit of width 1.0×10–5 cm is at
30º. Then wavelength of light used is,
Answer : Option B
Explaination / Solution:
λ = a sin θ = 1 × 10-7 x sin 30° =500
Å
Q7. A ray of light strikes a glass plate at an angle 60º. If the reflected and refracted rays are perpendicular to each other, the refractive index of the glass is,
Answer : Option A
Explaination / Solution:
n = tan ip
= tan (600) = √3
Q8. 
One of the of Young’s double slits is covered with
a glass plate as shown in figure. The position of central maximum will,
Answer : Option B
Explaination / Solution:
No Explaination.
Q9. Light transmitted by Nicol prism is,
Answer : Option C
Explaination / Solution:
No Explaination.
Q10. The transverse nature of light is shown in,
Answer : Option D
Explaination / Solution:
No Explaination.
