Define electromagnetic spectrum .

The electromagnetic spectrum is the continuous range of electromagnetic waves arranged in order of increasing frequency (decreasing wavelength).

State three properties shared by all electromagnetic waves.

All electromagnetic waves: are transverse waves; can travel through a vacuum ; travel at the same speed in a vacuum (the speed of light ).

Because electromagnetic waves are transverse, which five wave behaviours can they all show?

Transverse electromagnetic waves can reflect , refract , diffract , be polarised , and produce interference patterns.

The electromagnetic spectrum is arranged from the wavelength (lowest frequency) to the shortest wavelength (highest frequency).

The electromagnetic spectrum is arranged from the longest wavelength (lowest frequency) to the shortest wavelength (highest frequency).

True or False? The higher the frequency of electromagnetic radiation, the lower its energy.

False. The higher the frequency of electromagnetic radiation, the higher its energy.

Name three types of electromagnetic radiation that are highly ionising and harmful to living cells.

Ultraviolet (UV) , X-rays and gamma rays are highly ionising and can damage cells and tissues, causing cancer.

Define polarisation .

Polarisation is when the oscillations of a wave are restricted to a single plane, still perpendicular to the direction of energy transfer.

Why can transverse waves be polarised but longitudinal waves cannot?

Longitudinal waves oscillate parallel to the direction of travel, so restricting the plane has no effect. Transverse waves oscillate perpendicular to the direction of travel, so their plane of oscillation can be restricted.

Name a device used to polarise light and a device used to polarise microwaves.

A polarising filter is used to polarise light. A metal grille is used to polarise microwaves.

How does a metal grille polarise microwaves?

Free electrons in the metal bars cancel out (absorb) the electric field component parallel to the grille bars; the component perpendicular to the bars passes through.

When two polarising filters have their transmission axes to each other, the transmitted light intensity is at its maximum.

When two polarising filters have their transmission axes parallel to each other, the transmitted light intensity is at its maximum.

True or False? When two polarising filters have their transmission axes perpendicular to each other, the transmitted light intensity is at its maximum.

False. When the transmission axes are perpendicular , the transmitted light intensity is at its minimum (zero).

State three ways, other than passing through a polarising filter or grille, that light can become polarised.

Light can also be polarised by reflection , refraction and scattering .

Why must a TV or radio reception aerial be mounted in a specific orientation?

Broadcast signals are transmitted as either horizontally or vertically polarised waves, so the aerial must be aligned with the same polarisation to receive the signal correctly.

A LevelPhysicsOCRFlashcards4. Electrons, Waves & PhotonsEM Waves

EM Waves (OCR A Level Physics): Flashcards

Exam code: H556

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FrontThe Electromagnetic Spectrum
Define electromagnetic spectrum.

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Cards in this collection (15)

Define electromagnetic spectrum.
The electromagnetic spectrum is the continuous range of electromagnetic waves arranged in order of increasing frequency (decreasing wavelength).
State three properties shared by all electromagnetic waves.
All electromagnetic waves: are transverse waves; can travel through a vacuum; travel at the same speed in a vacuum (the speed of light).
Because electromagnetic waves are transverse, which five wave behaviours can they all show?
Transverse electromagnetic waves can reflect, refract, diffract, be polarised, and produce interference patterns.
The electromagnetic spectrum is arranged from the wavelength (lowest frequency) to the shortest wavelength (highest frequency).
The electromagnetic spectrum is arranged from the longest wavelength (lowest frequency) to the shortest wavelength (highest frequency).
True or False?
The higher the frequency of electromagnetic radiation, the lower its energy.
False.
The higher the frequency of electromagnetic radiation, the higher its energy.
Name three types of electromagnetic radiation that are highly ionising and harmful to living cells.
Ultraviolet (UV), X-rays and gamma rays are highly ionising and can damage cells and tissues, causing cancer.
Which equation links the speed of light to frequency and wavelength?
$c = f λ$
where c is the speed of light, $3.0 \times 10^{8} {m s}^{- 1}$ .
Define polarisation.
Polarisation is when the oscillations of a wave are restricted to a single plane, still perpendicular to the direction of energy transfer.
Why can transverse waves be polarised but longitudinal waves cannot?
Longitudinal waves oscillate parallel to the direction of travel, so restricting the plane has no effect. Transverse waves oscillate perpendicular to the direction of travel, so their plane of oscillation can be restricted.
Name a device used to polarise light and a device used to polarise microwaves.
A polarising filter is used to polarise light. A metal grille is used to polarise microwaves.
How does a metal grille polarise microwaves?
Free electrons in the metal bars cancel out (absorb) the electric field component parallel to the grille bars; the component perpendicular to the bars passes through.
When two polarising filters have their transmission axes to each other, the transmitted light intensity is at its maximum.
When two polarising filters have their transmission axes parallel to each other, the transmitted light intensity is at its maximum.
True or False?
When two polarising filters have their transmission axes perpendicular to each other, the transmitted light intensity is at its maximum.
False.
When the transmission axes are perpendicular, the transmitted light intensity is at its minimum (zero).
State three ways, other than passing through a polarising filter or grille, that light can become polarised.
Light can also be polarised by reflection, refraction and scattering.
Why must a TV or radio reception aerial be mounted in a specific orientation?
Broadcast signals are transmitted as either horizontally or vertically polarised waves, so the aerial must be aligned with the same polarisation to receive the signal correctly.

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