NEET Wave Optics — Set 19

Question 1

What is the shape of the wavefront after a plane wave passes through a thin prism?

Accepted Answer

A plane wave passing through a prism gets tilted due to the varying thickness, resulting in a tilted plane wavefront.

Question 2

What is the angular position of the first minimum in a single-slit diffraction pattern if the slit width is $ 8.0 \, \mu\text{m} $ and the wavelength is $ 640 \, \text{nm} $?

Accepted Answer

First minimum occurs at $ \sin \theta = \frac{\lambda}{a} $. $ \lambda = 6.4 \times 10^{-7} \, \text{m} $, $ a = 8.0 \times 10^{-6} \, \text{m} $. $ \sin \theta = \frac{6.4 \times 10^{-7}}{8.0 \times 10^{-6}} = 0.08 $, $ \theta = \sin^{-1}(0.08) \approx 4.6^\circ $.

Question 3

In a diffraction pattern, what happens to the angular width of the central maximum if the slit width is doubled?

Accepted Answer

Angular width of the central maximum is $ 2\theta = \frac{2\lambda}{a} $. If $ a $ is doubled, $ 2\theta $ is halved.

NEET Physics: Wave Optics — Practice Set 19

Q1. What is the shape of the wavefront after a plane wave passes through a thin prism?

Q2. What is the angular position of the first minimum in a single-slit diffraction pattern if the slit width is \( 8.0 \, \mu\text{m} \) and the wavelength is \( 640 \, \text{nm} \)?

Q3. In a diffraction pattern, what happens to the angular width of the central maximum if the slit width is doubled?

Q4. What is the intensity at a point in a double-slit experiment where the phase difference is \( 3\pi \), if the maximum intensity is \( 4I_0 \)?

Q5. What is the speed of light in a medium with refractive index 1.25, given the speed in vacuum is \( 3.0 \times 10^8 \, \text{m/s} \)?

Q6. What causes the intensity of light to be zero at certain points in a diffraction pattern?

Q7. What is the frequency of light with a wavelength of \( 510 \, \text{nm} \) in air, given the speed of light in air is \( 3.0 \times 10^8 \, \text{m/s} \)?

Q8. What is the distance of the fifth bright fringe from the central maximum in a double-slit experiment if \( \lambda = 490 \, \text{nm} \), \( d = 0.5 \, \text{mm} \), and \( D = 1.0 \, \text{m} \)?

Q9. What is the frequency of light with a wavelength of \( 600 \, \text{nm} \) in air, given the speed of light in air is \( 3.0 \times 10^8 \, \text{m/s} \)?

Q10. What is the condition for the fifth minimum in a single-slit diffraction pattern?