Infrared

4 marks · Normal

All objects emit infrared radiation. A hot stone is left to cool in a cold room.

(a)

Explain why the stone emits more infrared radiation as its temperature increases.

[2 marks]

(b)

Name two household appliances or devices that use infrared radiation for their operation.

[2 marks]

Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.

Show answer

(a) — · must show hotter object = more infrared emitted, energy emission increases with temperature

(b) — · must show Accept any two: toaster, grill, electric fire, remote control, security camera, heat lamp

Common mistakes: Confusing visible and infrared; Omitting that all objects emit

Show mark scheme and worked solution

Marking points

B1 (a) · 1 mark · States that hotter objects emit more infrared radiation.

B2 (a) · 1 mark · Explains that as temperature increases, energy emitted as infrared increases.

B3 (b) · 1 mark · Names one correct device/appliance using infrared (e.g. toaster, remote control).

B4 (b) · 1 mark · Names a second different device/appliance using infrared.

Worked solution

a) As the temperature of the stone increases, it emits more energy per second as infrared radiation because hotter objects radiate more infrared.

b) Examples: A toaster and a remote control use infrared radiation.