Question 1

Which experiment first demonstrated the wave nature of light?

Accepted Answer

Young’s double-slit experiment

Question 2

What is a diffraction grating?

Accepted Answer

An opaque screen with many closely spaced slits

Question 3

When laser light passes through two closely spaced slits and shines on a screen, what is observed?

Accepted Answer

Interference fringes

Question 4

The spreading of waves behind an aperture is:

Accepted Answer

More for long wavelengths, less for short wavelengths

Question 5

Which of the following best describes the wave model of light?

Accepted Answer

It explains how light spreads out and how superposition of multiple light waves causes interference.

Question 6

In a double-slit experiment, the condition for constructive interference (bright fringes) is:

Accepted Answer

$$ \Delta r = m \lambda $$

Question 7

A laboratory experiment produces a double-slit interference pattern on a screen. If the screen is moved farther away from the slits, the fringes will be:

Accepted Answer

Farther apart

Question 8

If green light (shorter wavelength than red) is used in a double-slit experiment, with all other parameters unchanged, the bright fringes will be:

Accepted Answer

Closer together

Question 9

In a double-slit experiment, if the slit separation $$d is $$decreased, what happens to the fringe spacing $$\Delta y$$?

Accepted Answer

The fringes get farther apart

Question 10

The intensity of the central maximum in a double-slit experiment is proportional to the square of the amplitude. If the amplitude is doubled, by what factor does the intensity increase?

Accepted Answer

4

Question 11

A diffraction grating is illuminated with light of two slightly different wavelengths. What is observed on the screen?

Accepted Answer

Two sets of bright fringes at slightly different angles

Question 12

If the number of slits in a diffraction grating is increased (with slit spacing unchanged), what happens to the interference pattern?

Accepted Answer

The fringes stay in the same positions but get brighter and narrower

Question 13

For a single-slit diffraction pattern, the condition for the first dark fringe is:

Accepted Answer

$$ a \sin 	heta = \lambda $$

Question 14

A laboratory experiment produces a single-slit diffraction pattern on a screen. If the slit is made narrower, the bright fringes will be:

Accepted Answer

Farther apart

Question 15

In a single-slit diffraction experiment, the slit width $$a$$ and the light wavelength $$\lambda$$ satisfy which relationship for visible diffraction to occur?

Accepted Answer

$$ \lambda \u003c a $$

Question 16

A Michelson interferometer is used with red light ($$\lambda = 650 nm) $$and produces a bright spot at the center. If the wavelength is doubled to $$1300 nm$$, with no other changes, the center will be:

Accepted Answer

Either bright or dark, but there’s not enough information to say which

Question 17

Which of the following is a real-world application of diffraction gratings?

Accepted Answer

Spectroscopy for analyzing the composition of materials

Question 18

A peacock feather appears colorful due to:

Accepted Answer

Reflection gratings formed by parallel rods of melanin

Question 19

Which principle explains why every point on a wavefront can be considered a source of secondary wavelets?

Accepted Answer

Huygens’ Principle

Question 20

In a realistic double-slit experiment, the overall intensity pattern is modulated by:

Accepted Answer

The single-slit diffraction pattern of each slit

Chapter 33: Wave Optics – Diffraction, Interference, and Applications

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