Thermal-Wave-Light

Very small pollen grains are suspended in water. A bright light shines from the side. When looked at through a microscope, small specks of light are seen to be moving in a random, jerky manner.

What are the moving specks of light ?

• pollen grains being hit by other pollen grains

• pollen grains being hit by water molecules

• water molecules being hit by other water molecules

• water molecules being hit by pollen grains

Two square sheets of metal, P and Q, are heated to the same temperature. The metal sheets are shown. Sheet Q is emitting more radiation than sheet P.

Which statement explains this?

• Dull black surfaces are better conductors of radiation.

• Dull black surfaces are better emitters of radiation

• The surface area of Q is larger than that of P

• White surfaces are better absorbers of radiation

An object is placed in front of a thin converging lens. The diagram shows the paths of two rays from the top of the object. An image of the object is formed on a screen to the right of the lens.

How does this image compare with the object?

• It is larger and inverted.

• It is larger and the same way up.

• It is smaller and inverted.

• It is smaller and the same way up.

A ray of light is incident on a plane mirror. A student measures the angle of incidence i and the angle of reflection r. The student varies the angle of incidence and then plots a graph of r against i.

What does the graph look like?

• 
• 
• 
• 

• 8.0 ms

• 16 ms

• 8.0 s

• 16 s

a) A machine delivers a hot drink in a plastic cup, which is uncomfortably hot to hold.

Explain how using the holder makes it more comfortable to hold the cup

b) A student carries out experiments on the cooling of the hot drink described in (a), with and without the holder in place. He finds that the holder only reduces the rate of cooling slightly. Suggest and explain another action that reduces the rate of cooling more effectively.

c) State the method of thermal energy transfer from a star through the vacuum of space.