Physics Y9 CA1

What is dispersion?

The separation of white light into colours because each colour refracts by a different amount.

What does a prism do to white light?

It refracts it and separates it into a spectrum of colours.

Which colour refracts the least in a prism?

Red

Which colour refracts the most in a prism?

Violet

What is the order of colours in the visible spectrum (least to most refraction)?

Red, Orange, Yellow, Green, Blue, Indigo, Violet.

What determines the colour of visible light?

Its wavelength or frequency

What is the wavelength range of visible light?

Approximately 400 nm (violet) to 750 nm (red).

Do all colours of visible light travel at the same speed?

Yes, they all travel at the speed of light (3 × 10⁸ m/s).

What is the wave equation?

v = f × λ.

How do you find frequency from wavelength?

f = v / λ

How do you find wavelength from frequency?

λ = v / f

What is the frequency of red light with wavelength 6.8 × 10⁻⁷ m?

f = 4.4 × 10¹⁴ Hz. (Using f = v/λ with v = 3 × 10⁸ m/s.)

What is the wavelength of Radio 4 broadcasting at 198 kHz?

λ = 1500 m. (λ = v/f.)

What is the wavelength of X-rays with frequency 1.0 × 10¹⁹ Hz?

λ = 3 × 10⁻¹¹ m

What is the wavelength of microwaves with frequency 1 × 10¹¹ Hz?

λ = 0.003 m or 3 mm.

What is the Doppler effect?

The apparent change in frequency when there is relative motion between the source and observer.

What happens to frequency when the source moves towards the observer?

Frequency increases

What happens to wavelength when the source moves towards the observer?

Wavelength decreases.

What happens to frequency when the source moves away from the observer?

Frequency decreases

What happens to wavelength when the source moves away from the observer?

Wavelength increases

Does wave speed change during the Doppler effect?

No, wave speed stays the same

What does a ripple tank show?

Wave patterns such as reflection, refraction, wavelength, and wavefronts.

How do you measure the frequency in a ripple tank?

Using the frequency of the power supply.

How do you measure wavelength in a ripple tank?

Measure the distance between wavefronts.

How do you measure wave speed in a ripple tank?

Measure how far a wavefront travels in a given time.

What happens when waves reflect in a ripple tank?

They bounce off a barrier at the same angle.

What happens when waves move into shallow water in a ripple tank?

They slow down and their wavelength decreases (refraction).

Do waves change frequency when they refract?

No, only wavelength and speed change.

What is a transverse wave?

A wave where vibrations are perpendicular to the direction of energy transfer.

Give examples of transverse waves.

Light waves, water waves, waves on strings or ropes.

What is a longitudinal wave?

A wave where vibrations are parallel to the direction of energy transfer.

What are compressions?

Regions of high pressure in a longitudinal wave.

What are rarefactions?

Regions of low pressure in a longitudinal wave.

What is the wavelength of a longitudinal wave?

The distance between two compressions or two rarefactions.

What is reflection?

A wave bouncing off a surface.

What is refraction?

A wave changing direction when entering a new medium.

Why do echoes occur?

Because sound waves reflect off surfaces.

What is the time period of a wave?

The time taken for one full wave.

What is the formula connecting time period and frequency?

T = 1/f

What is frequency?

Number of waves per second; measured in hertz (Hz).

What is amplitude?

The height of the wave from the central/rest position.

What is wavelength?

The distance from one peak to the next peak.

What is wave velocity?

The speed that the wave travels; measured in m/s.

What is a wavefront?

A line joining points that are at the same stage in a wave (e.g., all peaks).

Are wavefronts perpendicular or parallel to wave direction?

Perpendicular

Do waves transfer matter?

No, they transfer energy without transferring matter.

Why is light faster than sound?

Light travels at 3 × 10⁸ m/s; sound travels at about 340 m/s.

Why do we see lightning before hearing thunder?

Because light travels much faster than sound.