Physics Paper 2

What does a.c. stand for?

Alternating current.

What is the nucleus of an atom made of?

Protons and neutrons only.

What is an isotope?

Atoms of the same element with the same number of protons but different numbers of neutrons.

What is the nucleus of hydrogen-3 (³₁H) made of?

One proton and two neutrons.

What happens to an electron when it emits electromagnetic radiation?

It moves from a higher energy level to a lower energy level.

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

It emits electromagnetic radiation.

What causes the lines in the emission spectrum of hydrogen?

Electrons move from higher energy levels to lower energy levels and emit light.

What is an artificial satellite?

A human-made object placed in orbit around a planet or another body.

What is a natural satellite?

A naturally occurring object that orbits a planet, such as the Moon orbiting Earth.

What is nuclear fusion?

The process in which light nuclei join together to form a heavier nucleus, releasing energy.

What is nuclear fission?

The process in which a heavy nucleus splits into smaller nuclei, releasing energy.

What causes a nebula to collapse and form a star?

Gravity.

What is a nebula?

A mass of interstellar dust and gas.

What is a main sequence star?

A star that is stable because the inward gravitational force is balanced by the outward force from the core.

What is a red giant?

A low-temperature star with a diameter much larger than the Sun.

What is a white dwarf?

A star that has used most of its nuclear fuel and has collapsed.

What is a black dwarf?

A star formed from a white dwarf that no longer produces radiation.

What force causes a nebula to collapse?

Gravity.

In the Sun's current stage, how does the gravitational force compare with the outward force?

They are equal.

What is red-shift?

Light from a distant galaxy is observed at a longer wavelength than the same light measured on Earth.

What does red-shift suggest about a galaxy?

The galaxy is moving away from Earth.

What does a greater red-shift indicate about a galaxy?

It is moving away faster and is generally further away.

Which theory is supported by the red-shift of distant galaxies?

The Big Bang theory.

What is the Big Bang theory?

The theory that the Universe began from a very small, hot and dense state and has been expanding.

What is the cosmic microwave background radiation evidence for?

The Big Bang theory.

What is the relationship between wavelength and frequency for electromagnetic waves?

As wavelength increases, frequency decreases.

What is the order of the electromagnetic spectrum from longest to shortest wavelength?

Radio, microwaves, infrared, visible light, ultraviolet, X-rays, gamma rays.

What is the order of the electromagnetic spectrum from shortest to longest wavelength?

Gamma rays, X-rays, ultraviolet, visible light, infrared, microwaves, radio waves.

What is always true about the speed of electromagnetic waves in air?

They travel at approximately the same speed, regardless of their frequency.

What happens to frequency when wavelength increases, if wave speed stays constant?

Frequency decreases.

What is the relationship between wave speed, frequency and wavelength?

Wave speed = frequency × wavelength.

How do you calculate wavelength?

Wavelength = wave speed ÷ frequency.

How do you calculate frequency?

Frequency = wave speed ÷ wavelength.

A sound wave has a frequency of 500 Hz and travels at 330 m/s. Calculate its wavelength.

330 ÷ 500 = 0.66 m.

Red light travels through glass at 2.0 × 10⁸ m/s and has a wavelength of 4.33 × 10⁻⁷ m. Calculate its frequency.

(2.0 × 10⁸) ÷ (4.33 × 10⁻⁷) = 4.6 × 10¹⁴ Hz to 2 significant figures.

What type of wave is sound?

A longitudinal wave.

What is a longitudinal wave?

A wave where particles vibrate parallel to the direction of energy transfer.

What is a transverse wave?

A wave where particles vibrate perpendicular to the direction of energy transfer.

What is amplitude?

The maximum displacement of a point on a wave from its resting position.

What is wavelength?

The distance between two corresponding points on consecutive waves, such as one peak to the next.

What type of wave is light?

An electromagnetic transverse wave.

What happens to the frequency of sound when it travels from air into water?

It stays the same.

What happens to the speed of sound when it travels from air into water?

It increases.

What happens to the wavelength of sound when it travels from air into water?

It increases because its speed increases while its frequency stays the same.

What happens to the frequency of a wave when it enters a different medium?

It stays the same.

What is ultrasound?

Sound with a frequency higher than the upper limit of human hearing.

How can ultrasound be used to measure the depth of the seabed?

A pulse is sent towards the seabed and the time taken for its echo to return is measured.

Why might a ship receive more than one echo from an ultrasound pulse?

The pulse can reflect from different objects, such as fish and the seabed.

How do you calculate distance travelled by a wave?

Distance = speed × time.

An ultrasound pulse takes 0.60 s to travel to the seabed and back. Its speed is 1500 m/s. Calculate the seabed depth.

(1500 × 0.60) ÷ 2 = 450 m. Divide by 2 because the pulse travels there and back.

A seabed is 3600 m below a ship. Ultrasound travels at 1500 m/s. Calculate the time for the pulse to return.

Total distance = 3600 × 2 = 7200 m. Time = 7200 ÷ 1500 = 4.8 s.

What is reflection?

When a wave hits a surface and bounces back.

What is refraction?

The change in direction of a wave when it enters a different medium because its speed changes.

What is the normal in a ray diagram?

An imaginary line drawn at 90° to the surface where the ray hits.

What is the angle of incidence?

The angle between the incident ray and the normal.

What is the angle of reflection?

The angle between the reflected ray and the normal.

What is the law of reflection?

The angle of incidence equals the angle of reflection.

What is the incident ray?

The ray of light travelling towards a surface.

What is the refracted ray?

The ray of light that changes direction as it enters a different medium.

What happens to a ray of light when it enters glass from air at an angle?

It slows down and bends towards the normal.

What happens to a ray of light when it leaves glass and enters air at an angle?

It speeds up and bends away from the normal.

How can you investigate reflection using a plane mirror?

Place a mirror on paper, shine a narrow ray of light at it using a ray box, mark the incident and reflected rays, remove the mirror and draw the rays, then measure the angles using a protractor.

What should be measured in an experiment investigating reflection?

The angle of incidence and the angle of reflection.

What should a reflection experiment show?

The angle of incidence is equal to the angle of reflection.

How can you improve a reflection experiment?

Repeat measurements using several different angles of incidence and calculate mean values.

What is a convex lens?

A lens that is thicker in the middle and makes parallel light rays converge.

What is a concave lens?

A lens that is thinner in the middle and makes parallel light rays diverge.

What is the principal focus of a convex lens?

The point where parallel rays of light meet after passing through the lens.

What happens when white light passes through a red filter?

Red light is transmitted and most other colours are absorbed.

What happens when white light passes through a blue filter?

Blue light is transmitted and most other colours are absorbed.

What happens when blue light passes through a red filter?

No light is transmitted, so it appears dark.

Why does a red object appear black in blue light?

It absorbs blue light and cannot reflect red light because there is no red light available.

Why does a white object appear blue in blue light?

It reflects the blue light shining on it.

Why can a white number be difficult to see on a red shirt under red light?

The red shirt and white number both reflect red light, so there is little or no colour contrast.

What colour does a red shirt appear under blue light?

Black, because it absorbs blue light.

What colour does a white number appear under blue light?

Blue, because it reflects blue light.

What is red-shift in astronomy?

The wavelength of light from a distant galaxy is longer than the wavelength from the same source measured on Earth.

What happens to the wavelength of light when a galaxy moves away from Earth?

The wavelength increases.

What is the relationship between the amount of red-shift and the speed a galaxy is moving away?

Greater red-shift means the galaxy is moving away faster.

What is velocity?

Speed in a given direction.

What is acceleration?

The rate of change of velocity.

How do you calculate acceleration?

Acceleration = change in velocity ÷ time.

How do you calculate force?

Force = mass × acceleration.

How do you calculate work done?

Work done = force × distance.

What is the unit of work done?

Joules (J).

A force of 1200 N moves an object 16 m. Calculate the work done.

1200 × 16 = 19 200 J.

A car has a mass of 1800 kg and accelerates at 3 m/s². Calculate the force.

1800 × 3 = 5400 N.

A car changes velocity by 18 m/s in 0.15 s. Calculate its deceleration.

18 ÷ 0.15 = 120 m/s².

What is thinking distance?

The distance travelled by a vehicle during the driver's reaction time.

What is braking distance?

The distance travelled by a vehicle after the brakes are applied until it stops.

What is stopping distance?

Thinking distance + braking distance.

What factors increase thinking distance?

Higher speed, alcohol, drugs, tiredness and distractions.

What factors increase braking distance?

Higher speed, wet or icy roads, worn tyres and worn brakes.

What effect does drinking alcohol have on thinking distance?

It increases thinking distance because reaction time becomes longer.

What effect does drinking alcohol have on braking distance?

No effect directly, because braking distance depends on the vehicle and road conditions.

What effect does higher speed have on thinking distance?

It increases thinking distance.

What effect does higher speed have on braking distance?

It increases braking distance.

What effect does a wet road have on thinking distance?

No effect.

What effect does a wet road have on braking distance?

It increases braking distance because there is less friction between the tyres and road.

A car has a braking force of 5600 N and a braking distance of 20 m. Calculate the work done by the brakes.

5600 × 20 = 112 000 J.