NEET Wave Optics — Set 12

Question 1

What characteristic of light waves allows a convex lens to transform a plane wave into a converging spherical wave?

Accepted Answer

The wave nature enables the lens to delay the wavefront variably across its surface, curving it into a spherical shape that converges at the focal point.

Question 2

What is the condition for the fourth secondary maximum in a single-slit diffraction pattern?

Accepted Answer

Secondary maxima occur at $ \theta \approx \frac{(n + \frac{1}{2})\lambda}{a} $. For the fourth secondary maximum, $ n = 4 $, $ \theta \approx \frac{9\lambda}{2a} $.

Question 3

What is the intensity of light after passing through a polaroid rotated at $ 30^\circ $ relative to the initial polarization direction, if the intensity after the first polaroid is $ I_0 $?

Accepted Answer

Using Malus’ law, $ I = I_0 \cos^2 \theta $. For $ \theta = 30^\circ $, $ \cos 30^\circ = \frac{\sqrt{3}}{2} $, $ I = I_0 \left(\frac{\sqrt{3}}{2}\right)^2 = I_0 \times \frac{3}{4} = 0.75 I_0 $.

NEET Physics: Wave Optics — Practice Set 12

Q1. What characteristic of light waves allows a convex lens to transform a plane wave into a converging spherical wave?

Q2. What is the condition for the fourth secondary maximum in a single-slit diffraction pattern?

Q3. What is the intensity of light after passing through a polaroid rotated at \( 30^\circ \) relative to the initial polarization direction, if the intensity after the first polaroid is \( I_0 \)?

Q4. What is the intensity of light after passing through two polaroids with pass-axes at \( 60^\circ \), if the intensity after the first is \( I_0 \)?

Q5. In a single-slit diffraction pattern, what happens to the intensity of the central maximum if the slit width is doubled?

Q6. What is the distance of the second dark fringe from the central maximum in a double-slit experiment if \( \lambda = 700 \, \text{nm} \), \( d = 0.35 \, \text{mm} \), and \( D = 1.5 \, \text{m} \)?

Q7. In a double-slit experiment, if \( \lambda = 580 \, \text{nm} \), \( d = 0.25 \, \text{mm} \), and \( D = 2.5 \, \text{m} \), what is the fringe width?

Q8. What ensures that light rays from a point source appear to diverge uniformly in all directions?

Q9. What is the path difference for the second bright fringe in a double-slit experiment?

Q10. In a double-slit experiment, if the wavelength is tripled, what happens to the fringe width?