K A Tsokos Solutions for Chapter: Waves, Exercise 6: Exam-style questions

Which of the following does not apply to longitudinal waves?

Interference is observed with two identical coherent sources. The intensity of the waves at a point of constructive interference is $I$. What is the intensity when one source is removed?

Unpolarized light of the intensity $I_0$ is incident on two polarisers, one behind the others, with parallel transmission axes. The first polarizer is rotated by ${30}^{°}$ clockwise and the second ${30}^{°}$counter-clockwise. What is the intensity transmitted?

A pipe of length $8.0 m$ is open at one end and closed at the others. The speed of sound is $320 m{s}^{-1}$. Which is the lowest frequency of a standing wave that can be established within this pipe?

Describe what is meant by polarised light.

Unpolarised light of intensity $320 {\mathrm{Wm}}^{-2}$ is incident on the first of three polarisers that are one behind the other. The first and third polarisers have vertical transmission axes. The middle polariser's transmission axis is rotated by an angle $\theta$ to the vertical. The transmitted intensity is $10 {\mathrm{Wm}}^{-2}$. Determine $\theta$.

Partially polarised light is a combination of completely unpolarised light and light that is polarised. Partially polarised light is transmitted through a polariser. As the polariser is rotated by $360°$, the ratio of the maximum to the minimum transmitted intensity is $7$.

Determine the fraction of the beam's intensity that is due to the polarised light.

A person is sitting behind a vertical glass wall. The person cannot be clearly seen because of the glare of reflections from the glass wall. Suggest how the use of a polariser makes it easier to see the person more clearly.