Topic 3.3: Wave Phenomena Questions

A parallel beam of monochromatic light travels through air and strikes the flat surface of a glass block.

The wavefronts make an angle of 58° with the surface in the air.

Inside the glass, the wavefronts make an angle of 33° with the surface.

Which expression gives the refractive index of the glass for this light?

State what is meant by the superposition of two waves.

State what is meant by the diffraction of a wave.

State what is meant by the refractive index of a transparent material.

Light enters a block of transparent plastic from a vacuum and slows to a speed of 2.0 × 10⁸ m s⁻¹ inside it.

The speed of light in a vacuum is 3.0 × 10⁸ m s⁻¹.

Show that the refractive index of the plastic is 1.5.

The refractive index of ice is 1.31.

Deduce the speed of light inside the ice, taking the speed of light in a vacuum to be 3.0 × 10⁸ m s⁻¹.

Describe the pattern of light seen on a screen when monochromatic, coherent light is passed through two narrow, closely spaced slits.

A row of straight waves on the surface of water approaches a harbour wall that has a single narrow opening.

Identify, from the list below, the one change that would make the waves spread out MORE on the far side of the opening: (i) widening the opening; (ii) increasing the wavelength of the waves; (iii) increasing the frequency of the waves.

State the equation that relates the fringe spacing in a double-slit pattern to the wavelength of the light, the slit separation and the slit-to-screen distance, defining each symbol you use.

Two slits 0.40 mm apart are lit by light of wavelength 6.4 × 10⁻⁷ m.

Calculate, in radians, the angular separation between two neighbouring bright fringes (maxima) of the pattern.

A particular type of optical-fibre glass has a refractive index of 1.62.

Estimate the critical angle for a boundary between this glass and the surrounding air (refractive index 1.0).

In an experiment a narrow beam of light travels from air into a liquid.

The angle of incidence in the air is measured as 60° and the angle of refraction in the liquid as 35°, both from the normal.

Two small loudspeakers, S₁ and S₂, are driven by the same signal generator so that they emit sound that is coherent and in phase, with a wavelength of 0.40 m.

A microphone is placed at point P.

The distance S₁P is 2.10 m and the distance S₂P is 2.70 m.

Because P is closer to S₁, the wave from S₁ arrives with an amplitude of 5.0 mm at P, while the wave from S₂ arrives with an amplitude of 3.0 mm at P.

What is the amplitude of the resultant sound wave at P?

In a double-slit experiment the bright fringes are 3.0 mm apart when the screen is 1.5 m from the slits.

The screen is then moved to 2.5 m from the slits, with the slits and the wavelength unchanged.

Calculate the new fringe spacing.

Two coherent radio aerials emit waves of wavelength 2.5 m.

At a receiver the wave from the nearer aerial has travelled 30.0 m and the wave from the farther aerial has travelled 40.0 m.

Show that the receiver is at a position of constructive interference.

Sound travels at about 340 m s⁻¹.

A loudspeaker emits a low note of frequency 85 Hz and a high note of frequency 3400 Hz through the same open doorway, which is about 1 m wide.

Calculate the wavelength of each note, and explain which note can be heard more easily by a listener standing to one side of the doorway (out of the direct line of the speaker).

Two coherent sources emit waves of wavelength 0.030 m.

At a point the waves from the two sources have a path difference of 0.045 m.

Identify whether the waves arrive in phase or in antiphase at that point.

A red laser (wavelength ≈ 7 × 10⁻⁷ m) is shone first through a slit 2 mm wide and then through a slit 0.05 mm wide.

Explain why a clear spread-out pattern of light is seen on a distant screen only for the narrower slit.

Two coherent loudspeakers a fixed distance apart emit the same steady note.

A student walks slowly along a line in front of them.

Describe what the student hears and explain, in terms of path difference, why the loudness changes.

A ray of light travels from water (refractive index 1.33) into a layer of oil (refractive index 1.47) floating on top of it.

It strikes the water–oil boundary at an angle of incidence of 35° to the normal.

Calculate the angle of refraction in the oil, and state whether the ray bends toward or away from the normal.