Transverse Waves: EM Spectrum & Polarisation (CIE AS Physics)

Two lasers are set up to pass through a vacuum. One laser emits red light; the other emits green light.

 Which property of the two lasers are different?

The wavelength of light emitted by a laser is 600 nm.

 Which of the following is the distance in number of wavelengths, that is travelled by light in one second?

Waves of the electromagnetic spectrum travel through a vacuum at speed c and with a wavelength λ and frequency f

 Which of the following describes the speed and wavelength when the frequency is   ?

	λ	c
A
B
C
D

The diameter of a nucleus and the wavelength of an electromagnetic wave are in the same order of magnitude.

 In which region of the electromagnetic spectrum would that wavelength occur?

R is a source emitting infra-red radiation and S is a source emitting ultra-violet radiation. The table suggests the wavelengths for R and S.

 Which row is correct?

Which statement would be deduced from a table of wavelengths of the waves in the electromagnetic spectrum?

A telescope detects electromagnetic radiation with wavelengths 2 cm.

Which type of telescope is it ?

A linearly polarised electromagnetic beam has an intensity of 16 W m^–2 with an angle of incidence of 45° to the vertical.

 What is the intensity of the transmitted beam?

Unpolarised light of intensity I₀ is incident on a polariser with a vertical transmission axis. The transmitted light is incident on a sheet of material X. After transmission through X the intensity of light is 

 It is suggested that X could be

The quality of the sound produced by a portable radio can be improved by changing the orientation of the aerial.

 Which statement will correctly describe the explanation of this improvement?

A beam of unpolarised light is incident on the first of two parallel polarisers. The transmission axis of the two polarisers are initially parallel.

The first polariser is now rotated about the direction of the incident beam by an angle smaller than 90°.

 Which row in the table describes the changes to the intensity and polarisation of the transmitted light?

Unpolarised light is incident on the surface of a transparent medium. The reflected light is completely plane polarised.

 Which option correctly describes the refracted light?

Unpolarised light of intensity I₀ is incident on a polariser that has a vertical transmission axis, as shown in the diagram below.

Which graph shows the intensity of the transmitted light ?

Plane-polarised light of amplitude a is passed through a polarising filter. The amplitude of the light emerging is a cos θ.

 The intensity of the incident ray is I

 What is the intensity of the emerging light when θ is 60˚?

A person wearing polarising sunglasses stands at the edge of a pond in bright sunlight.

The surface of the pond is flat, and the person has a line of sight to the surface of angle θ. The refractive index of the pond water is n.

 What is the value of θ for which the light would be a minimum when it reaches the persons eye?

Unpolarised light is incident on a polariser. The light transmitted by the first polariser is then incident on a second polariser. The polarising axis of the second sheet is 60˚ to that of the first.

 The intensity emerging from the second polariser is I₂.

 Which of the following gives the intensity incident on the first polariser?

A vertical aerial transmits radio waves that have been plane-polarised. The receiving aerial is tilted from the vertical at an angle θ. The emitted wave is in a plane perpendicular to the direction of arrival and arrive with an amplitude A.

 Which of the following expressions is proportional to the power delivered by the aerial?

Unpolarised light of intensity I₀ is incident on the first of two polarising sheets. Initially the planes of polarisation of the sheets are perpendicular.

 Which sheet must be rotated and by what angle θ, so that light intensity     can emerge from the second sheet ?

	Rotated sheet	Angle θ of rotation
A	1 or 2
B	1 or 2
C	2 only
D	1 only

The diagram below shows a ray of unpolarised light with an intensity of 72 W m⁻² passing through three polarising films, P₁, P₂ and P₃.

The polarising axis of each polarising film is shown by an arrow. The polarising film P₁ and P₂ are fixed, with their axis of polarisation at 30˚ to one each other.

 If the light emerging from the third filter has an intensity of 13.5 W m⁻² what is angle θ ?

The angle between a polariser and analyser is 30°. The intensity of light transmitted by the analyser is greater that the intensity transmitted by the polariser.

 How much smaller is the intensity transmitted?