Black body radiation

This question is about both infrasound and ultrasound.

Which of these is a frequency of infrasound ?

Figure 1 shows a technician standing in front of a wall.

The technician has a device that can emit and detect ultrasound.

The device emits a pulse of ultrasound towards the wall and detects the echo of the pulse a short time later.

The wall is 7.6 m from the device.

The speed of ultrasound in air is 330 m / s.

Calculate the time between the emission of the pulse and the detection of the echo.

Explain why humans cannot hear infrasound.

Describe how the power of a lens is related to its focal length and the shape of the lens.

Give one example of a virtual image that a lens could produce.

Give one example of a real image that a lens could produce.

A student investigates what happens when a ray of light shines into a semicircular block made of transparent plastic.

The ray meets the straight edge at an angle of 20°, as shown in Figure 13.

The student gradually increases the angle at the straight edge from 20° to 50° and observes what happens to the ray of light.

The critical angle for the transparent plastic is 38°.

Describe what you would expect to happen to the ray of light as the angle at the straight edge increases from 20° to 50°.

You may add to the diagram in Figure 13 to help your answer.

The asteroid Ceres orbits the Sun between Mars and Jupiter.

During its orbit, Ceres receives electromagnetic radiation from the Sun.

The average temperature of Ceres is constant.

Explain why the average temperature of Ceres remains constant.

Figure 9 shows a metal cube filled with hot water.

Four sides of the cube have different surfaces, as shown in Figure 9.

The four surfaces are at the same temperature.

The thermal energy radiated by each side of the box is measured using a thermal energy detector connected to a millivoltmeter.

The detector is moved to get a reading of the thermal energy emitted from each side of the box.

Figure 10 shows the table of results.

Suggest a possible millivoltmeter reading for the shiny black surface.

State what must be kept the same to take the measurement for each surface.

Suggest why the cube is placed on a block of wood.

A hot surface emits radiation of different wavelengths.

The graph in Figure 11 shows how the intensity of the radiation emitted changes with the wavelength.

Describe how intensity changes with wavelength in Figure 11.

A student does an experiment to determine the critical angle for glass.

The student shines a ray of light into a semicircular glass block and measures the angles i and r, as shown in Figure 14.

The ray of light does not change direction when it enters the glass block at point X.

Which of these explains why the ray of light does not change direction when it enters the glass block at point X.

The student repeats the procedure for different values of angle i.

Figure 15 is a graph of the student’s results.

Describe how the student should use the graph in Figure 15 to determine the critical angle for glass.

Figure 16 shows two iron spheres, P and Q, near to a radiant heater. P is painted black and Q is painted white.

Each sphere is the same distance away from the heater.

The spheres have the same radius.

The heater is switched on and the spheres heat up.

The temperature of each sphere is monitored.

Explain why the temperature of sphere P increases at a faster rate than the temperature of sphere Q.

The heater remains switched on.

Figure 17 shows how the temperature of sphere P changes with time.

Explain why the temperature of P reaches a constant value, even though the heater remains switched on.

The Asteroid Belt is part of our Solar System.

Vesta is an asteroid in the Asteroid Belt.

Vesta orbits the Sun between the orbits of

Vesta has an orbital speed of 1.9 × 10⁴ m/s.

Vesta travels a distance of 2.2 × 10¹² m when it orbits the Sun once.

Calculate the time taken for Vesta to orbit the Sun once.

Explain why Vesta is accelerating even when it is travelling at a constant speed.

Energy is transferred from the Sun to Vesta by radiation.

Explain why the temperature on Vesta does not continue to rise, even though it is absorbing energy from the Sun.

The distance between Vesta and the Sun is 2.4 AU.

1 AU is the distance between the Earth and the Sun.

The intensity of the Sun’s radiation reaching the Earth is 1400 W/m².

1 W = 1 J/s

The intensity of the Sun’s radiation at a distance, d, from the Sun is given by the equation

where K always has the same value.

State the unit of K.

Calculate the intensity of the radiation from the Sun at Vesta.

Draw one line from each use of wave to the matching electromagnetic wave.

One line has been drawn for you.

Ultraviolet light has a higher frequency than infrared light.

Which of these colours of visible light has the highest frequency?

Figure 1 shows how the brightness of a source of light changes with wavelength.

Describe how the brightness changes with wavelength.

Figure 4 shows two light rays hitting a glass lens.

On Figure 4, draw the two light rays after they leave this lens.

Figure 4

Figure 5 shows two light rays hitting a different glass lens.

On Figure 5, draw the two light rays after they leave this lens.

A lens has a focal length of 25 cm.

Calculate the power of the lens.

Use the equation

power of the lens =_........ dioptres

Figure 6 shows two solid metal balls, P and Q.

P and Q are made from the same metal and have the same radius.

P is painted black and Q is painted white.

Each ball is heated to a different temperature.

The balls then cool in the same room.

The graph in Figure 7 shows how the temperature of each ball changes with time.

Use the graph in Figure 7 to determine the time when P and Q were at the same temperature.

Show your working on the graph.

Which of these temperatures is most likely to be room temperature, as shown by the graph in Figure 7?

Explain why the curve for P is different from the curve of Q. Use information from Figure 6 and Figure 7 to help your answer.

A copper can, painted black, contains boiling water at 100 °C.

The can is left to cool and a measurement of the water temperature is taken every 5 minutes.

Figure 3 shows the measurements.

Two points, shaded in the table, have not been plotted.

Plot these two points on the graph, in Figure 4.

One of the points on the graph in Figure 4 is anomalous.

Circle the anomalous point.

Draw the best fit curve on the graph in Figure 4.

An identical can contains the same amount of boiling water.

This can has a shiny silver surface.

The measurements are repeated with this can and a new curve is drawn.

State how the cooling curve would be different from the curve in the graph in Figure 4.

Figure 5 is a graph showing the intensity–wavelength curves for two hot objects, L and M.

Estimate the wavelength where the intensity is at a maximum for each of the objects.

wavelength at maximum intensity for object L =_........ µm

wavelength at maximum intensity for object M =_........ µm

State, with a reason, which object is the hotter object.

A student investigates how different surfaces radiate energy as they cool.

Figure 9 shows some of the apparatus used in a part of the investigation.

Describe how the student could collect data to show how the rate of cooling of the container and water change with time.

Figure 10 is a graph of intensity against wavelength for the electromagnetic radiation emitted by a halogen lamp.

Describe how the intensity of the radiation varies with wavelength in Figure 10.

Figure 11 is a graph of temperature against time for a halogen lamp for the first 120 ms after it has been switched on.

Calculate the gradient of the graph at a time of 30 ms.

State the unit.

Explain why the temperature of the lamp rises and then remains at a constant value.