P13 - EM waves Flashcards
What are electromagnetic (EM) waves? Name all of their types in decreasing λ:
transverse waves that form a continuous spectrum, where all of the λ travel at a constant speed through a vacuum
RP10 - How can you investigate the amount of IR radiation radiated from different surfaces?
-fill Leslie cube with hot water
-use IR detector 20cm away from surface to record temperature at regular intervals with a stopwatch
-draw a curve for that material on a graph of T vs time
-repeat with other sides of the Leslie cube and draw 1 curve per material
A Leslie cube is a box with different materials on each side
How can radio waves be produced, and what can they do to circuits?
-oscillations in electrical circuits
-when absorbed they may induce an AC with the same frequency as the radio wave itself
The remote control transmits radio waves to the car aerial - describe what happens in the car’s circuit when it absorbs them:
-alternating current is induced in the circuit
-with the same frequency as the radio wave
What are some differences between a radio wave and a sound wave?
give comparative answers in an exam
-radio is transverse
-radio travels at a much higher speed
-radio does not need a medium to travel through (because it is electromagnetic, and not mechanical)
Mechanical (eg sound, seismic) waves require a medium, EM (radio, gamma) waves do not
What effect does UV radiation have on the body?
causes skin to age prematurely and increase the risk of skin cancer
UV radiation is non-ionising
How do X-rays and gamma rays affect the body?
it is ionising radiation, so it penetrates cells and causes genetic mutations, which can increase the risk of cancer
Give some uses of radio waves:
TV and AM/FM radio
Give some uses of microwaves:
satellite communications and cooking food
Give some uses of IR:
electrical heaters, cooking food, IR cameras
Give some uses of visible light:
fibre optics communications
Give some uses of UV light:
energy efficient lamps, sun tanning
Give some uses of X-rays and gamma rays:
medical imaging and treatments
Explain how the properties of X-rays make them suitable for bone imaging:
-they pass through soft tissue
-but they are absorbed by bones
The cloud has a higher albedo than the ground.
Why does area A cool faster than area B at night?
-at night, more radiation is emitted by the Earth than absorbed from space
-cloud reflects radiation emitted from the ground back towards Earth
-at A, there is no cloud cover so a larger proportion of radiation will be emitted into space
