Paper 1 Knowledge Gaps: Content Flashcards
What are the four types of decay?
- gamma
- beta plus
- beta minus
- alpha
Define alpha decay
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
What is the effect of alpha decay on
a) the atomic number?
b) the mass number?
a) decreases by 2
b) decreases by 4
How strong is alpha decay?
- highly ionising
- weakly penetrating
Define beta minus decay
If a nucleus has too many neutrons, a neutron will turn into a proton and emit a fast-moving electron
What is the electron emitted in beta minus decay called?
beta minus (β−) particle
What is the effect of beta minus decay on
a) the atomic number?
b) the mass number?
a) increase by one
b) remains the same
How strong are both of the beta decays?
medium ionising, medium penetration
Define beta plus decay
If a nucleus doesn’t have enough neutrons, a proton will turn into a neutron and emit a fast-moving positron
What is another name for a positron?
beta plus (β+) particle
What is the effect of beta plus decay on
a) the atomic number?
b) the mass number?
a) decreases by one
b) stays the same
Define gamma decay
A nucleus will often still have excess energy after emitting an alpha/beta particle and so energy will be emitted as a gamma ray
What is the effect of gamma ray emission on
a) the atomic number?
b) the mass number?
No effect on either
How strong are gamma rays?
- highly penetrating
- weakly ionising
Define half life
The amount of time it takes for half of the sample of unstable nuclei to halve
What is the equation to calculate how many nuclei remain after a certain amount of time concerning half life?
net decline = (initial number x number after x half lives)/ initial number
Describe the life cycle of a star that has a mass similar to solar mass
- Nebula
- protostar
- main sequence star
- red giant
- white dwarf
Describe a nebula
Giant cloud of hydrogen gas and dust
How does a nebula become a protostar?
- force of gravity pulls particles closer
- until hot ball of gas is formed
- known as a protostar
How does a protostar become a main sequence star?
- 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
How does a main sequence star turn into a red giant?
- 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
How does a red giant star turn into a white dwarf?
Once all of the reactions are over, the star contracts and cools into a white dwarf = core collapses completely
What is the life cycle of stars that have a mass larger than solar mass?
- nebula
- protostar
- main sequence star
- red supergiant
- supernova
- neutron star or a black hole
What is the difference between a red supergiant and a red giant?
A red supergiant is much larger than a red giant
How does a red supergiant form a supernova?
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
How is infrasound used to investigate earthquakes?
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
What are the two waves produced by earthquakes?
P waves and S waves
What are the differences between P waves and S waves?
- P waves: longitudinal: can pass through solids and liquids
- S waves: transverse; can only pass through solids
Describe how the human ear detects sound
- Sound waves enter the ear canal
- sound wave hits the eardrum, which vibrates at the same frequency as the wave
- tiny bones vibrate and amplify the vibrations
- vibration of bones transmitted to the fluid in the inner ear
- tiny hairs within cochlea detect the vibrations and create electrical impulses
- impulses travel along auditory nerve to the brain, giving the sensation of sound
Why is a sound wave a pressure wave?
The compressions and rarefactions cause changes in pressure, which vary in time with the wave
How is ultrasound used in foetal scanning?
- An ultrasound detector produces and detects a beam of ultrasound waves into the body
- The ultrasound waves are reflected back to the detector by different boundaries between tissues in the path of the beam
- For example, the boundary between fluid and soft tissue or tissue and bone
What are the two main discoveries made due to seismic waves?
- 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 - 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
Define shadow zone
Area on the Earth’s surface where P waves nor S waves can be detected
What is Earth’s temperature dependant on?
- 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
What happens when light and IR radiation are absorbed by the Earth’s surface?
- planet’s internal energy increases
- surface gets hotter
- some energy transferred to the atmosphere by conduction and convection
What happens when the Earth radiates lower frequency IR radiation?
- some absorbed by greenhouse gases
- greenhouse gases emit IR radiation in all directions; some out into space and some back towards earth
