Electromagnetic Waves Flashcards

All 32 cards in this deck

Are electromagnetic waves transverse or longitudinal?

Transverse — all of them.
e.g. x-rays and microwaves are both transverse waves.

Which property is the same for all electromagnetic waves travelling in a vacuum?

Speed.
e.g. x-rays and microwaves always have the same speed in a vacuum.

What do all electromagnetic waves transfer from a source to an observer?

Energy.
e.g. a fire mostly emits infrared, which transfers thermal energy to a person's hands.

True or false? All electromagnetic waves have the same frequency and wavelength in a vacuum.

False. Only the speed is the same for all EM waves in a vacuum; frequency and wavelength are different for each group.

What is the normal in the refraction core practical?

A line drawn at 90° to the surface of the block at the point where the ray hits it.

Which way does a light ray bend as it enters a glass block from air?

e.g. a ray hitting the surface at 40° to the normal

Towards the normal — the angle of refraction is smaller than the angle of incidence (smaller than 40°).

Name the seven groups of the electromagnetic spectrum in order from longest to shortest wavelength.

Radio waves, microwaves, infrared, visible light, ultraviolet, x-rays, gamma rays.

Across the electromagnetic spectrum, what happens to wavelength as frequency increases?

Wavelength decreases.
The spectrum is continuous from radio waves to gamma rays.

List the colours of the visible spectrum in order of increasing frequency.

Red, orange, yellow, green, blue, indigo, violet.
Red has the longest wavelength and lowest frequency.

Which part of the electromagnetic spectrum can the human eye detect?

Visible light only — our eyes detect just a limited range of frequencies.

What harmful effect can excessive exposure to microwaves have on the body?

Internal heating of body cells.

What harmful effect can excessive exposure to infrared have on the body?

Skin burns.

What harmful effects can excessive exposure to ultraviolet have on the body?

Damage to surface cells and eyes, leading to skin cancer and eye conditions.

What harmful effect can excessive exposure to x-rays and gamma rays have on the body?

Mutation or damage to cells in the body, which can cause cancer.
They are ionising.

How does the potential danger of an electromagnetic wave change across the spectrum?

It increases as frequency increases.
e.g. gamma rays are far more dangerous than radio waves.

Give two uses of microwaves.

Cooking, communications, satellite transmissions.

Give two uses of infrared.

Thermal imaging (night-vision cameras), cooking, television remote controls, optical fibres, security systems.

Give two uses of ultraviolet.

Detecting forged banknotes, disinfecting water, security marking, fluorescent lamps.

Give two uses of x-rays.

Medical x-rays to see broken bones, airport security scanners, observing the internal structure of objects (e.g. cracks in metals).

Give two uses of gamma rays.

Sterilising food and medical equipment, detecting cancer and treating it (radiotherapy).

Give two uses of radio waves.

Broadcasting (radio and television), communications, satellite transmissions.

What can changes in atoms and their nuclei do to electromagnetic radiation?

They can generate radiation over a wide frequency range, and they can be caused by the absorption of a range of radiations.

Which type of electromagnetic radiation is emitted by radioactive nuclei?

Gamma rays.

What happens to an electron in an atom when it absorbs electromagnetic radiation?

It moves to a higher energy level (further from the nucleus).

What happens when an electron moves from a higher energy level to a lower one?

It emits electromagnetic radiation.

True or false? Electromagnetic waves need a medium to travel through.

False. All electromagnetic waves can travel through a vacuum, at the same speed.

True or false? Infrared has a higher frequency than ultraviolet.

False. Ultraviolet has the higher frequency; infrared sits on the longer-wavelength side of visible light.

Which part of the electromagnetic spectrum in sunlight should people protect themselves from, and with what two precautions?

Ultraviolet — use sunscreen and sunglasses (or cover the skin).

Why should a thin ray of light be used in the refraction core practical?

A thin ray can be traced with a sharp pencil line, so the angles are measured more accurately.

True or false? In the refraction core practical, the angle of refraction is measured from the surface of the glass block.

False. It is measured from the normal.

Which way does a light ray bend as it leaves a glass block and passes into air?

Away from the normal. The angle of refraction in the air is bigger than the angle of incidence inside the glass.

Give two uses of visible light.

Seeing (vision), lighting/illumination, photography.