NEET Wave Optics — Set 9

Question 1

What type of wave is light, based on the direction of its electric field relative to its propagation direction?

Accepted Answer

Light is a transverse wave because its electric field oscillates perpendicular to the direction of propagation.

Question 2

What is the distance of the fourth dark fringe from the central maximum in a double-slit experiment if $ \lambda = 610 \, \text{nm} $, $ d = 0.3 \, \text{mm} $, and $ D = 1.5 \, \text{m} $?

Accepted Answer

Dark fringe position $ x_n = \frac{\left(n + \frac{1}{2}\right) \lambda D}{d} $. For the fourth dark fringe, $ n = 3 $. $ \lambda = 6.1 \times 10^{-7} \, \text{m} $, $ d = 3.0 \times 10^{-4} \, \text{m} $, $ D = 1.5 \, \text{m} $. $ x_3 = \frac{\left(3 + \frac{1}{2}\right) \times 6.1 \times 10^{-7} \times 1.5}{3.0 \times 10^{-4}} = \frac{3.5 \times 9.15 \times 10^{-7}}{3.0 \times 10^{-4}} = 1.0675 \times 10^{-2} \, \text{m} \approx 10.7 \, \text{mm} $.

Question 3

What is the wavelength of light in a medium with refractive index 1.6 if its wavelength in vacuum is $ 640 \, \text{nm} $?

Accepted Answer

Wavelength in a medium $ \lambda_m = \frac{\lambda_{\text{vacuum}}}{n} $. Given $ \lambda_{\text{vacuum}} = 640 \, \text{nm} $, $ n = 1.6 $, $ \lambda_m = \frac{640}{1.6} = 400 \, \text{nm} $.

NEET Physics: Wave Optics — Practice Set 9

Q1. What type of wave is light, based on the direction of its electric field relative to its propagation direction?

Q2. What is the distance of the fourth dark fringe from the central maximum in a double-slit experiment if \( \lambda = 610 \, \text{nm} \), \( d = 0.3 \, \text{mm} \), and \( D = 1.5 \, \text{m} \)?

Q3. What is the wavelength of light in a medium with refractive index 1.6 if its wavelength in vacuum is \( 640 \, \text{nm} \)?

Q4. What is the wavelength of light in a medium with refractive index 1.5 if its wavelength in air is \( 720 \, \text{nm} \)?

Q5. What is the refractive index of a medium if the critical angle for light passing into air is \( 42^\circ \)?

Q6. What is the intensity at a point in a double-slit experiment where the phase difference is \( \pi/4 \), if the maximum intensity is \( 4I_0 \)?

Q7. Why does the interference pattern disappear if the phase difference between two sources changes rapidly over time?

Q8. What type of wavefront emerges from a convex lens when a plane wave is incident on it?

Q9. What is the resultant amplitude of two coherent waves of amplitude \( a \) with a phase difference of \( 5\pi \)?

Q10. What is the refractive index of a medium if the speed of light in it is \( 2.4 \times 10^8 \, \text{m/s} \) and in vacuum is \( 3.0 \times 10^8 \, \text{m/s} \)?