Wave Optics Chapter-Wise Test 17

Correct answer Carries: 4.

Wrong Answer Carries: -1.

What property of light waves is responsible for the redistribution of energy into bright and dark regions during diffraction?

The superposition of secondary wavelets causes constructive and destructive interference, redistributing energy into bright and dark regions.

Speed change
Amplitude variation
Superposition
Frequency stability
3

Why does the intensity of light transmitted through two polaroids become zero when their axes are at 90° to each other?

The first polaroid aligns the electric field, and the second, perpendicular to it, blocks all components, as the cosine of 90° is zero in the intensity relation.

Wavelength doubles
Electric field component is blocked
Frequency decreases
Amplitude increases
2

What is the frequency of light with a wavelength of \( 460 \, \text{nm} \) in air, given the speed of light in air is \( 3.0 \times 10^8 \, \text{m/s} \)?

Frequency \( \nu = \frac{c}{\lambda} \).

\( \lambda = 4.6 \times 10^{-7} \, \text{m} \), \( c = 3.0 \times 10^8 \, \text{m/s} \).

\( \nu = \frac{3.0 \times 10^8}{4.6 \times 10^{-7}} \approx 6.52 \times 10^{14} \, \text{Hz} \).

\( 5.26 \times 10^{14} \, \text{Hz} \)
\( 6.52 \times 10^{14} \, \text{Hz} \)
\( 4.41 \times 10^{14} \, \text{Hz} \)
\( 5.88 \times 10^{14} \, \text{Hz} \)
2

What is the refractive index of a medium if the speed of light in it is \( 2.5 \times 10^8 \, \text{m/s} \) and in vacuum is \( 3.0 \times 10^8 \, \text{m/s} \)?

Refractive index \( n = \frac{c}{v} \).

\( c = 3.0 \times 10^8 \, \text{m/s} \), \( v = 2.5 \times 10^8 \, \text{m/s} \).

\( n = \frac{3.0 \times 10^8}{2.5 \times 10^8} = 1.2 \).

1.5
1.3
1.2
1.6
3

What is the fringe width in a double-slit experiment if \( \lambda = 590 \, \text{nm} \), \( d = 0.25 \, \text{mm} \), and \( D = 1.2 \, \text{m} \)?

Fringe width \( \beta = \frac{\lambda D}{d} \).

\( \lambda = 5.9 \times 10^{-7} \, \text{m} \), \( d = 2.5 \times 10^{-4} \, \text{m} \), \( D = 1.2 \, \text{m} \).

\( \beta = \frac{5.9 \times 10^{-7} \times 1.2}{2.5 \times 10^{-4}} = 2.832 \times 10^{-3} \, \text{m} = 2.83 \, \text{mm} \).

2.83 mm
2.36 mm
3.54 mm
1.18 mm
1

Why does the angle of refraction increase beyond 90° become impossible when light moves from a denser to a rarer medium?

Beyond the critical angle, the sine of the refraction angle exceeds 1, which is mathematically impossible, leading to total internal reflection.

Speed decreases
Sine exceeds unity
Frequency shifts
Amplitude drops
2

What is the speed of light in a medium with refractive index 1.8, given the speed in vacuum is \( 3.0 \times 10^8 \, \text{m/s} \)?

Speed in a medium \( v = \frac{c}{n} \).

Given \( n = 1.8 \), \( c = 3.0 \times 10^8 \, \text{m/s} \), \( v = \frac{3.0 \times 10^8}{1.8} \approx 1.67 \times 10^8 \, \text{m/s} \).

\( 1.67 \times 10^8 \, \text{m/s} \)
\( 2.0 \times 10^8 \, \text{m/s} \)
\( 1.5 \times 10^8 \, \text{m/s} \)
\( 3.0 \times 10^8 \, \text{m/s} \)
1

What determines the intensity of light in the wave picture?

In the wave picture, intensity is proportional to the square of the amplitude of the wave.

Frequency
Wavelength
Speed
Square of the amplitude
4

What is the frequency of light with a wavelength of \( 680 \, \text{nm} \) in air, given the speed of light in air is \( 3.0 \times 10^8 \, \text{m/s} \)?

Frequency \( \nu = \frac{c}{\lambda} \).

\( \lambda = 6.8 \times 10^{-7} \, \text{m} \), \( c = 3.0 \times 10^8 \, \text{m/s} \).

\( \nu = \frac{3.0 \times 10^8}{6.8 \times 10^{-7}} \approx 4.41 \times 10^{14} \, \text{Hz} \).

\( 5.26 \times 10^{14} \, \text{Hz} \)
\( 4.41 \times 10^{14} \, \text{Hz} \)
\( 5.0 \times 10^{14} \, \text{Hz} \)
\( 4.76 \times 10^{14} \, \text{Hz} \)
2

What ensures that light rays appear to travel in straight lines despite their wave nature?

The extremely small wavelength of light compared to everyday objects minimizes wave effects, making rectilinear propagation dominant in macroscopic observations.

High frequency
Constant speed
Large amplitude
Small wavelength
4

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