matter and radiation

What is the equation to work out specific charge

Charge / mass

What does a laser consist of

Photons of the same frequency

What is the power of a laser beam

The energy per second transferred by the photons

What is the equation for the power of a beam

Nhf where n is the number of photons in beam passing a fixed point each second

When does positron emission take place

When a proton changes into a neutron in an unstable nucleus with too many protons

What is given out during positron emission

• positron, neutrino and isotope with 1 less atomic number

What is rest energy

E0 =M0c2 where this is the mass of a stationary particle

What did diracs theory of antiparticles predict

That for every particle, there is a corresponding antiparticle that,

• annihilates the particle and itself if meet, converting their whole mass into photons

• Has exactly the same rest mass as the particle

• Has exactly opposite charge to the particle if it has charge

What is the process of pair production

Photon with sufficient energy passing near a nucleus or electron can suddenly change into a particle- antiparticle pair, which would then separate from each other

What is MeV into joules

1MeV = 1.60 ×10^-13

Define electron volt

The energy transferred when an electron is moved through a potential difference of 1 volt

When does annihilation occur

When a particle and its corresponding antiparticle meet and their mass is converted into radiation energy and two photons are produced in the process

Why is two photons instead of one produced in annihilation

As it cannot ensure a total momentum of 0 after the collision.

How do u find the minimum energy of each photon

By equating the energy of the two photons to the rest energy of particle 2hf=2E0

Ho d u find the minimum energy of photon needed ( pair production)

Hfmin= 2E0

What happens when a photon has less energy than the minimum photon energy

It cannot create a positron and an electron

What is a stable isotope

It has a nucleus that doesn’t disintegrate

What is the strong nuclear force

The force that holds the protons and neutrons in the nucleus together and its strong as it overcomes the electrostatic force of repulsion between the protons in the nucleus

What is the range for the strong nuclear force

3-4fm

What is the range of the attractive force for strong nuclear force

3-4fm - 0.5fm but anything less is repulsive forces that’s prevents the neutrons and protons being pushed together

What happens in beta decay

A fast moving electron/ beta particle is emitted as a result of the nucleus having too many neutrons so a neuron changes into a proton and an uncharged antineutrino is emitted as well

What is gamma radiation

Electromagnetic radiation is emitted by an unstable nucleus and happens with a nucleus with too much energy

What’s thee range for radio waves

>0.1 m

What is the range for microwaves

0.1m- 1mm

What is the range for infrared

1mm - 700nm

What is the range for visible light

700nm - 400nm

What is the range for ultraviolet

400nm-1nm

X-rays range

10nm-0.001nm

Gamma rays range

<1nm

What do electromagnetic waves consist of

• electric and magnetic waves travelling at right angles to each other in direction they are travelling

• In phase with each other

What are photons

Quanta of em waves

Equation for photon energy

E=Hf