IB Physics Topic C - Wave Behaviour Questionbank

A string of length $L = 1.0\ \text{m}$ is fixed at both ends and supports standing waves. The wave speed is $v = 120\ \text{m s}^{-1}$.

A light wave travels from air into glass.

A student shines a red laser onto a double slit and observes a pattern on a screen.

A spacecraft, while receding from Earth at $0.85c$, emits light at a rest frequency of $5.00 \times 10^{14}\ \text{Hz}$. An Earth-based observer detects a redshifted signal. The frequency received on Earth is approximately $1.42 \times 10^{14}\ \text{Hz}$.

(c) State the length of the tube in terms of the wavelength.

(a) Derive an expression for the wavelength $\lambda$ of the $n^\text{th}$ harmonic on the string.

(b) In a pipe that is closed at one end and open at the other, only certain harmonics are observed. Explain why some harmonics are missing in such a tube.

(c) Calculate the frequency of the fourth harmonic for the string.

(d) Sketch the standing wave pattern corresponding to the second and fourth harmonic on the string.

(a) Define the term “refraction”.

(b) State what happens to the speed of light as it enters the glass.

(c) Identify whether the wavelength increases, decreases, or remains constant in the glass.

(d) Suggest why the direction of the wave changes when it enters the glass.

(a) Sketch and label the intensity pattern observed.

(b) State how the fringe spacing would change if the slit separation is increased.

(c) Explain this change using the interference equation.

(a) Determine the wavelength of the light as measured in the rest frame of the spacecraft.

(b) Determine the observed wavelength of the light on Earth.

(c) Explain why the observed frequency on Earth is lower than the emitted frequency, even though the light travels at the same speed in all frames.