Waves

A wave travels from left to right. The particles of the medium vibrate up and down. State the wave type and explain your choice.

A cork is floating on still water. A single ripple passes the cork and reaches the far side of the tank. Describe what happens to the cork and explain what this shows about wave motion.

A compression pulse travels along a horizontal spring. Explain how the motion of one coil differs from the motion of the pulse, and identify two features that show the pulse is longitudinal.

A vibrating source produces $8.0$ complete waves each second. Calculate the period of the wave.

In a ripple tank, nine complete crest-to-crest intervals span $0.36\,\text{m}$. Five complete waves pass a marker in $2.0\,\text{s}$. Calculate the wavelength, frequency and wave speed.

A sound wave of frequency $2.40\,\text{kHz}$ travels from air, where its speed is $336\,\text{m s}^{-1}$, into water, where its speed is $1440\,\text{m s}^{-1}$. The frequency does not change. Calculate the wavelength in each medium and explain the change.

A light ray strikes a plane mirror at $35^\circ$ to the normal. State the angle of reflection and name the line from which both angles are measured.

At a boundary, $68\%$ of the incident wave energy is transmitted and $17\%$ is reflected. Calculate the percentage absorbed and describe the three outcomes at the boundary.

Describe an investigation that compares reflection of light from a smooth white tile and a rough white card. Include the measurements, control variables and how the results would be compared.

State the approximate lower and upper frequency limits of normal human hearing.

A loudspeaker receives an alternating electrical signal. Describe the sequence of energy transfers that produces sound in the room and then makes a listener's eardrum vibrate.

A hearing test shows that a person detects tones from $40\,\text{Hz}$ to $13\,\text{kHz}$ but not tones outside this interval. Explain why sound-to-vibration conversion in the ear produces this result and compare it with normal human hearing.

Define ultrasound and state what happens when an ultrasound pulse reaches a boundary between two different tissues.

An echo sounder sends a pulse vertically down through seawater. The echo returns after $0.084\,\text{s}$. The speed of sound in seawater is $1500\,\text{m s}^{-1}$. Calculate the water depth.

Seismic detectors on one side of Earth receive P-waves from an earthquake but receive no direct S-waves. Explain how the properties of P-waves and S-waves allow scientists to infer a liquid layer and locate boundaries inside Earth.

Name the electromagnetic wave immediately below visible light in frequency and the wave immediately above visible light in frequency.

An electromagnetic wave has frequency $5.0\times10^{10}\,\text{Hz}$. Calculate its wavelength in a vacuum and identify its region of the spectrum. Use $c=3.00\times10^8\,\text{m s}^{-1}$.

A radio signal has frequency $75\,\text{MHz}$ and a microwave signal has frequency $3.0\,\text{GHz}$. Calculate both wavelengths in air using $3.00\times10^8\,\text{m s}^{-1}$, then compare their speeds and wavelengths.

A light ray enters glass from air at an angle to the normal. State how the ray changes direction and name the line from which the angles are measured.

Higher only: parallel wavefronts are $2.4\,\text{cm}$ apart in medium A and $1.5\,\text{cm}$ apart in medium B. The frequency is unchanged. Calculate $v_B/v_A$ and explain what the wavefront spacing shows.

Plan an investigation to compare the rate of infrared emission from identical matt-black and shiny metal cans containing hot water. Include measurements, controls and a method of improving reliability.

A radiation dose is $180\,\text{mSv}$. Convert this dose to sieverts.

Procedure A gives a dose of $4.5\,\text{mSv}$ on each of six visits. Procedure B gives one dose of $18\,\text{mSv}$. Calculate the total dose for A and use the data to compare the radiation risk.

Higher only: a transmitter circuit oscillates at $92\,\text{MHz}$. Explain how it produces a radio wave and how a tuned receiving circuit can produce a signal at $92\,\text{MHz}$. Contrast this origin with the origin of gamma rays.

Name one electromagnetic wave used for each application: satellite communication, a thermal camera and medical imaging of bones.

Higher only: explain why an infrared camera can show warmer parts of a building and why visible light is unsuitable for measuring the same temperature pattern in darkness.

Higher only: a food manufacturer can heat a meal using microwaves or infrared radiation. Compare how the two waves heat the meal and explain why using both can improve the result.

A lens forms an image $3.6\,\text{cm}$ high from an object $1.2\,\text{cm}$ high. Calculate the magnification.

Describe how to construct a ray diagram for the image of an object formed by a concave lens, and state three properties of the image.

A lens produces a sharp image on a screen. The image is $7.2\,\text{cm}$ high and the magnification is $3.0$. Calculate the object height, identify the lens as convex or concave, and justify your choice.

Under white light, one opaque card reflects all visible wavelengths equally and another absorbs all visible wavelengths. State the colour of each card.

A red book is viewed in white light through a blue filter. Explain why the book appears very dark.

A surface strongly reflects green light, weakly reflects red light and absorbs blue light. Predict and explain its appearance under white light, through a green filter and through a red filter.

Two identical matt-black objects are at $35\,{}^\circ\text{C}$ and $75\,{}^\circ\text{C}$. State which emits more infrared radiation each second.

Identical hot-water cans have matt-black and polished-silver outer surfaces. Predict which can cools faster and explain the prediction in terms of infrared radiation.

A student uses an infrared lamp, four metal plates with different surface finishes and contact thermometers to compare absorption. Describe a valid method and explain how the data identify the best absorber.

State two features of the radiation emitted by an object that depend on the object's temperature.

Higher only: a body absorbs radiation at $480\,\text{W}$ and emits radiation at $530\,\text{W}$. Calculate the net rate of energy change and state what happens to its temperature.

Higher only: Earth receives an average solar power of $340\,\text{W m}^{-2}$. Initially $102\,\text{W m}^{-2}$ is reflected and $238\,\text{W m}^{-2}$ is emitted to space. The reflected power then decreases to $90\,\text{W m}^{-2}$ while the emitted power is initially unchanged. Calculate both initial and new net power, and explain the resulting temperature change.