AQA Topic 3 - Waves

Two points on a progressive wave have a phase difference of  $\frac{\pi}{6}$  rad

The speed of the wave is  $340\ m\ s^{-1}$ 

What is the frequency of the wave when the minimum distance between the two points is 0.12 m?

• 240 Hz

• 470 Hz

• 1400 Hz

• 2800 Hz

Which statement is correct about the properties of an unpolarised electromagnetic wave as it passes through a polariser?

• The wave remains unchanged

• The wave does not pass through the polariser

• The wave's electric field oscillates along the direction of travel

• The intensity of the wave is reduced

A uniform wire, fixed at both ends, is plucked in the middle so that it vibrates at the first harmonic as shown.

What is the phase difference between the oscillations of the particles at P and Q?

• Zero

• $\frac{\pi}{4}rad$

• $\frac{\pi}{2}rad$

• $\frac{3\pi}{4}rad$

Which row in the table shows the change in velocity, frequency and wavelength of an electromagnetic wave as it travels from an optically less dense to an optically more dense medium?

• A

• B

• C

• D

A stationary wave is set up on a stretched string of length l and diameter d.

Another stationary wave is also set up on a second string made from the same material and with the same tension as the first.

What length and diameter are required for the second string so that both strings have the same first-harmonic frequency?

• A

• B

• C

• D

A progressive wave of frequency 150 Hz travels along a stretched string at a speed of 30 m s^-1.

What is the phase difference between two points that are 50 mm apart on the string?

• zero

• 90^o

• 180^o

• 360^o

Two radio transmitters emit waves at a frequency of 1.4 MHz. A stationary wave is set up between the two transmitters due to the superposition of the radio waves.

What is the minimum distance between two nodes in the stationary wave?

• 107 m

• 214 m

• 428 m

• 857 m

Which of the following is correct for a stationary wave?

• Between two nodes the amplitude of the wave is constant.

• The two waves producing the stationary wave must always be 180° out of phase.

• The separation of the nodes for the second harmonic is double the separation of nodes for the first harmonic.

• Between two nodes all parts of the wave vibrate in phase.

The frequency of the first harmonic of a standing wave on a wire is f. The length of the wire and tension in the wire are both doubled.

What is the frequency of the first harmonic as a result?

• $\frac{f}{\sqrt{2}}$

• $f$

• $\sqrt{2}f$

• $2f$

A microwave transmitter is used to direct microwaves of wavelength 30 mm along a line XY. A metal plate is positioned at right angles to XY with its mid-point on the line, as shown.

When a detector is moved gradually along XY, its reading alternates between maxima and minima. Which one of the following statements is not correct?

• The distance between two minima could be 15 mm.

• The distance between two maxima could be 30 mm.

• The distance between a minimum and a maximum could be 30 mm.

• The distance between a minimum and a maximum could be 37.5 mm.