Wave Optics Chapter-Wise Test 7

Correct answer Carries: 4.

Wrong Answer Carries: -1.

What characteristic of light waves allows polarization to occur, distinguishing them from sound waves?

Light waves are transverse, with electric fields oscillating perpendicular to the propagation direction, enabling polarization, unlike longitudinal sound waves.

Transverse nature
High frequency
Longitudinal nature
Variable amplitude
1

Why does the intensity of light remain unaffected by changes in its speed during refraction?

Intensity depends on the square of the amplitude, which remains constant during refraction, while speed changes do not alter the energy per unit area.

Frequency increases
Amplitude remains constant
Wavelength stays the same
Phase shifts
1

What happens to the fringe width in a double-slit experiment if the slit separation is reduced to one-third?

Fringe width \( \beta = \frac{\lambda D}{d} \). If \( d \) is reduced to \( \frac{d}{3} \), \( \beta \) increases to \( 3\beta \), i.e., triples.

Reduces to one-third
Doubles
Remains the same
Triples
4

Why does light exhibit polarization only in specific directions when passing through a polaroid?

The polaroid aligns the electric field along its pass-axis, absorbing components in other directions, restricting polarization to that plane.

Wavelength variation
Speed reduction
Frequency alignment
Electric field alignment
4

What is the path difference for the first dark fringe in a double-slit experiment?

Destructive interference occurs at \( \Delta = \left(n + \frac{1}{2}\right)\lambda \). For the first dark fringe, \( n = 0 \), so \( \Delta = \frac{\lambda}{2} \).

\( \lambda \)
\( \frac{\lambda}{2} \)
\( 2\lambda \)
\( 0 \)
2

Why is the backwave not observed in the reflection of light according to the wave model?

The wave model assumes the amplitude of secondary wavelets is zero in the backward direction, though this is an ad-hoc assumption later justified by advanced wave theory.

Amplitude is zero in the backward direction
Light travels only forward
Reflection cancels the backwave
Frequency doubles in reflection
1

What happens to the fringe width in a double-slit experiment if both the slit separation and screen distance are doubled?

Fringe width \( \beta = \frac{\lambda D}{d} \). If \( D \) and \( d \) are both doubled, \( \beta = \frac{\lambda (2D)}{2d} = \frac{\lambda D}{d} \), so it remains the same.

Doubles
Halves
Triples
Remains the same
4

What property of light ensures that the time taken from an object point to its image point is the same along any ray path in a lens system?

The principle that light travels such that the optical path length (or time) is equal along all rays explains this, as the slower speed in a denser medium balances the shorter path.

Frequency
Equal travel time along rays
Amplitude
Wavelength
1

What happens to the fringe width in a double-slit experiment if the distance between the slits and the screen is tripled?

Fringe width \( \beta = \frac{\lambda D}{d} \). If \( D \) is tripled, \( \beta \) triples.

Halves
Remains the same
Doubles
Triples
4

What is the distance of the second bright fringe from the central maximum in a double-slit experiment if \( \lambda = 670 \, \text{nm} \), \( d = 0.6 \, \text{mm} \), and \( D = 1.8 \, \text{m} \)?

Bright fringe position \( x_n = \frac{n \lambda D}{d} \). For the second bright fringe, \( n = 2 \).

\( \lambda = 6.7 \times 10^{-7} \, \text{m} \), \( d = 6.0 \times 10^{-4} \, \text{m} \), \( D = 1.8 \, \text{m} \).

\( x_2 = \frac{2 \times 6.7 \times 10^{-7} \times 1.8}{6.0 \times 10^{-4}} = 4.02 \times 10^{-3} \, \text{m} = 4.02 \, \text{mm} \).

3.0 mm
5.0 mm
4.02 mm
2.0 mm
3

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