Paper 1 Knowledge Gaps: Content

Question 1

What are the four types of decay?

Answer 1

• gamma
• beta plus
• beta minus
• alpha

Question 2

Define alpha decay

Answer 2

If the nucleus is unstably large, it will emit a ‘package’ of two protons and two neutrons called an alpha particle
–> this is also a helium-4 nucleus

Question 3

What is the effect of alpha decay on
a) the atomic number?
b) the mass number?

Answer 3

a) decreases by 2
b) decreases by 4

Question 4

How strong is alpha decay?

Answer 4

• highly ionising
• weakly penetrating

Question 5

Define beta minus decay

Answer 5

If a nucleus has too many neutrons, a neutron will turn into a proton and emit a fast-moving electron

Question 6

What is the electron emitted in beta minus decay called?

Answer 6

beta minus (β−) particle

Question 7

What is the effect of beta minus decay on
a) the atomic number?
b) the mass number?

Answer 7

a) increase by one
b) remains the same

Question 8

How strong are both of the beta decays?

Answer 8

medium ionising, medium penetration

Question 9

Define beta plus decay

Answer 9

If a nucleus doesn’t have enough neutrons, a proton will turn into a neutron and emit a fast-moving positron

Question 10

What is another name for a positron?

Answer 10

beta plus (β+) particle

Question 11

What is the effect of beta plus decay on
a) the atomic number?
b) the mass number?

Answer 11

a) decreases by one
b) stays the same

Question 12

Define gamma decay

Answer 12

A nucleus will often still have excess energy after emitting an alpha/beta particle and so energy will be emitted as a gamma ray

Question 13

What is the effect of gamma ray emission on
a) the atomic number?
b) the mass number?

Answer 13

No effect on either

Question 14

How strong are gamma rays?

Answer 14

• highly penetrating
• weakly ionising

Question 15

Define half life

Answer 15

The amount of time it takes for half of the sample of unstable nuclei to halve

Question 16

What is the equation to calculate how many nuclei remain after a certain amount of time concerning half life?

Answer 16

net decline = (initial number x number after x half lives)/ initial number

Question 17

Describe the life cycle of a star that has a mass similar to solar mass

Answer 17

1. Nebula
2. protostar
3. main sequence star
4. red giant
5. white dwarf

Question 18

Describe a nebula

Answer 18

Giant cloud of hydrogen gas and dust

Question 19

How does a nebula become a protostar?

Answer 19

• force of gravity pulls particles closer
• until hot ball of gas is formed
• known as a protostar

Question 20

How does a protostar become a main sequence star?

Answer 20

• density of the protostar increases
• resulting in more frequent collisions between the particles
• = temperature increases
• thermal expansion from fusion reactions occur within its core and the force of gravity keeps the star in equilibrium

Question 21

How does a main sequence star turn into a red giant?

Answer 21

• main sequence star runs out of gas to fuse = no equilibrium
• this will cause the star to collapse
• which will increase the pressure and temperature of the core, allowing for heavier elements to form

Question 22

How does a red giant star turn into a white dwarf?

Answer 22

Once all of the reactions are over, the star contracts and cools into a white dwarf = core collapses completely

Question 23

What is the life cycle of stars that have a mass larger than solar mass?

Answer 23

1. nebula
2. protostar
3. main sequence star
4. red supergiant
5. supernova
6. neutron star or a black hole

Question 24

What is the difference between a red supergiant and a red giant?

Answer 24

A red supergiant is much larger than a red giant

Question 25

How does a red supergiant form a supernova?

Answer 25

Once all of the fusion has happened, it is too massie to be stable so the star collapses, rebounds on its scentre and produces a supernova

Question 26

How is infrasound used to investigate earthquakes?

Answer 26

On the opposite side of an earthquake, only the P waves can be detected, suggesting that the core of the earth is liquid since no S waves can penetrate it

Question 27

What are the two waves produced by earthquakes?

Answer 27

P waves and S waves

Question 28

What are the differences between P waves and S waves?

Answer 28

• P waves: longitudinal: can pass through solids and liquids
• S waves: transverse; can only pass through solids

Question 29

Describe how the human ear detects sound

Answer 29

1. Sound waves enter the ear canal
2. sound wave hits the eardrum, which vibrates at the same frequency as the wave
3. tiny bones vibrate and amplify the vibrations
4. vibration of bones transmitted to the fluid in the inner ear
5. tiny hairs within cochlea detect the vibrations and create electrical impulses
6. impulses travel along auditory nerve to the brain, giving the sensation of sound

Question 30

Why is a sound wave a pressure wave?

Answer 30

The compressions and rarefactions cause changes in pressure, which vary in time with the wave

Question 31

How is ultrasound used in foetal scanning?

Answer 31

1. An ultrasound detector produces and detects a beam of ultrasound waves into the body
2. The ultrasound waves are reflected back to the detector by different boundaries between tissues in the path of the beam
3. For example, the boundary between fluid and soft tissue or tissue and bone

Question 32

What are the two main discoveries made due to seismic waves?

Answer 32

1. On the opposite side of the Earth to an earthquake, only P-waves are detected, not S-waves, this suggests:
   -The mantle is solid – this is because both types of wave can pass through it
   -The outer core of the Earth is liquid – hence no S-waves can penetrate it
2. Refractions between layers cause two shadow zones, where no P-waves are detected, this suggests:
   The inner core is solid – this is due to the size and positions of these shadow zones which indicate large refraction taking place

Question 33

Define shadow zone

Answer 33

Area on the Earth’s surface where P waves nor S waves can be detected

Question 34

What is Earth’s temperature dependant on?

Answer 34

• concentration of greenhouse gases
• rates of which light and IR radiation are:
  —> absorbed by the Earth’s surface and atmosphere
  —> emitted by the Earth’s surface and atmosphere

Question 35

What happens when light and IR radiation are absorbed by the Earth’s surface?

Answer 35

• planet’s internal energy increases
• surface gets hotter
• some energy transferred to the atmosphere by conduction and convection

Question 36

What happens when the Earth radiates lower frequency IR radiation?

Answer 36

• some absorbed by greenhouse gases
• greenhouse gases emit IR radiation in all directions; some out into space and some back towards earth