Section 3: Waves

Question 1

Define amplitude, frequency, wavelength and period of a wave

Answer 1

Wavelength: The distance between one point on a wave and the same point on the next wave
Frequency: The number of waves per second
Amplitude: The amplitude is the distance between the line of the direction of travel and the furthest point the it vibrates away from the line
Period of a wave: Time taken for one complete wave

Question 2

Understand that waves transfer energy and information without transferring matter

Answer 2

A wave is a transfers energy, but it doesn’t carry particle.

Question 3

Know and use the relationship between the speed, frequency and wavelength of a wave:

Answer 3

wave speed = frequency × wavelength

Question 4

Use the relationship between frequency and time period:

Answer 4

Frequency = 1 / time period

Question 5

Identify the order of the electromagnetic and explain some of the uses of electromagnetic radiations

Answer 5

radio waves: broadcasting and communications
microwaves: cooking and satellite transmissions infrared: heaters and night vision equipment
visible light: optical fibers and photography ultraviolet: fluorescent lamps
x-rays: observing the internal structure of objects and materials and medical applications
gamma rays: sterilizing food and medical equipment

Question 6

Understand the detrimental effects of excessive exposure of the human body to electromagnetic waves and describe simple protective measures against the risks.

Answer 6

microwaves: internal heating of body tissue
infrared: skin burns
ultraviolet: damage to surface cells and blindness
gamma rays: cancer, mutation

Question 7

Define reflection, refraction and diffraction

Answer 7

Reflection: Light hitting a reflective surface will ‘bounce’ back from the surface
Refraction: Light waves change speed when they pass through objects of different densities, this causes them to change direction. When they return to theoriginaldensity they will continue in the original direction.
Diffraction: When light meats a barrier, it will carry on through the gap and spread out in the area beyond.

Question 8

Describe experiments to investigate the refraction of light, using rectangular blocks, semicircular blocks and triangular prisms

Answer 8

Place a block of glass on apieceof paper, drawing an outline.
At one point, draw the normal line.
Draw a line at 30 degrees to the normal line, shine a ray of light down this line.
Draw a line where the light comes out the other side. Connect the two lines, drawing the refracted ray.
Measure the angle of the emergent ray.

Question 9

Know and use the relationship between refractive index, angle of incidence and angle of refraction:

Answer 9

N = sin I / sin R

Question 10

Describe an experiment to determine the refractive index of glass, using a glass block

Answer 10

Shine a ray of light through a glass block,measurethe angle of incidence and the angle of refraction.

Question 11

Describe the role of total internal reflection in transmitting information along optical fibres and in prisms

Answer 11

Beyond the critical angle, light will be reflected back into the medium they came from at the same angle. In this way they are trapped in the medium.
By reflecting light past its critical angle you can make it travel through a medium to send information: this is done in optical fibres.

Question 12

Explain the meaning of critical angle c

Answer 12

The critical angle is the point at which light doesn’t leave a transparent material, but runs parallel to the opposite side of the block

Question 13

Know and use the relationship between critical angle and refractive index:

Answer 13

Sin C = 1 / N

Question 14

Understand the difference between analogue and digital signals

Answer 14

Analog singles can exists in almost infinite different forms where as digital can either be on or off

Question 15

Describe the advantages of using digital signals rather than analogue signals

Answer 15

Digital signals carry more information then analog information they also retain there quality over longer distances then analogue

Question 16

Describe how digital signals can carry more information

Answer 16

Digital signals carry information in a binary format, as either 1 or 0 (On or Off)

Question 17

Understand that sound waves are longitudinal waves

Answer 17

Sound waves are longitudinal and they can be refracted reflected and diffracted

Question 18

Know the frequency range for human hearing

Answer 18

The range of human hearing is 20 Hz – 20,000 Hz

Anything above this is called ultrasound, anything below is called infra sound

Question 19

Understand how an oscilloscope and microphone can be used to display a sound wave

Answer 19

A microphone detects sound waves, it can feed this information into an oscilloscope which will display it as a wave (or straight line.)

Question 20

Describe an experiment using an oscilloscope to determine the frequency of a sound wave

Answer 20

Have an noise made into a microphoneattachedto an oscilloscope, for example have someone try to sing a note. See how many oscillations there are per second, this will be your frequency. Try changing the pitch of the note and see it the number of oscillations per second changes.

Question 21

Relate the pitch of a sound to the frequency of vibration of the source

Answer 21

The higher the pitch the higher the temperature

Question 22

Relate the loudness of a sound to the amplitude

Answer 22

The higher the amplitude, the higher sound, as it has more penetrating power through the air

Question 23

Understand the difference between longitudinal and transverse waves

Answer 23

Transverse: Particles of medium move at right angles to the direction in which the wave transfers energy. EG Sound
Longitudinal: Particles of a medium move perpendicularly to the direction which the waves are transferred. E.G EM waves