P3 Edexcel Revision

Front 1

What is Radiation?

Back 1

Radiation is energy emitted for a source...

Front 2

What factors do the intensity of radiation depend on?

Back 2

1. the distance from the radiation source.
2.the medium which it passes through.

Front 3

Explain these factors?

Back 3

1. The intensity increases as the distance decreases. So the closer you get to the radiation source the more intense it will be.
2. intensity of the radiation decreases as the medium which it passes though get more dense. this is because, unless the radiation passes through a vacuum, it will lose energy and be absorbed by the medium its passing through meaning the intensity will decrease.

Front 4

What is the relationship between intensity and energy it has?

Back 4

The more intense the radiation is, the more power it has and therefore the more energy transferred when it hits an object.

Front 5

using the intensity equation calculate:
the intensity of a bulb 200w light bulb that spreads over a surface area of 2m squared?

Back 5

I=P/A
therefore..
I=200/2
I=100 w/m squared

Front 6

What makes a nucleus unstable?

Back 6

-Too many neutrons
-Too few neurons
-heavy nuclei/ so too much N or P+
-too much energry

Front 7

What is neutron rich?

Back 7

Have many neutrons than protons in their nucleus

Front 8

What is neutron poor?

Back 8

Too many protons than neutrons n the ir nucleus

Front 9

What causes Beta- decay?

Back 9

-Too many neutrons
-emission of an electron from the nucleus
-when isotopes are neutron rich
- when a nucleus ejects a beta particle, one of the N changes to P+
-Nucleon number stays the same
-proton number increases by 1

Front 10

What is Beta+ decay?

Back 10

-too few neutrons
-emission of a positron from the nucleus
-when isotopes are neutron poor
-when a nucleus ejects a beta+ particle, one of the P changes into a N
-Nucleon number stays the same
-Proton number decreases by 1

Front 11

What is Alpha decay?

Back 11

-Heavy nuclei (more than 82 protons)
-Nuclei too massive to be stable
-proton No. decreases by 2
-Nucleon No. decreases by 4
-Alpha is emitted.

Front 12

What is gamma radiation decay?

Back 12

After alpha and beta decay, the nucleus often has excess energy, it loses his energy by emitting gamma rays.
-there is no change in proton or nucleon number

Front 13

What is the curve of stability?

Back 13

-any isotope that doesn't lie on the curve is unstable.
-unstable=radioactive
-isotope that lies above the curve has too many neutrons to be stable B-
-isotope that lie below the curve has too few neutrons to be stable B+

Front 14

equation for momentum

Back 14

momentum=mass x velocity

Front 15

what is "momentum is always conserved"

Back 15

total momentum before is = to total momentum afterwards.

Front 16

3 situations of momentum?

Back 16

1. collision and bouncing off each other
2. collision and joining together
3.explosion, shot and recoil

Front 17

what is elastic collision?

Back 17

momentum is conserved and kinetic energy is conserved. so no energy is dissipated (lost) as heat, sound etc.

Front 18

what is inelastic collision?

Back 18

Momentum is conserved. some kinetic energy is converted into other form during collision and may be dissipated.

Front 19

What are the relative masses for an atoms particle?

Back 19

P=1
N=2
E-=1/2000

Front 20

What are the relative charge for an atoms particle?

Back 20

P=+1
N=0
E=-1

Front 21

Properties of an alpha radiation?

Back 21

Helium nucleus 4 2 he
charge= +2e
slow and heavy
Strongly ionising
Stopped by paper skin and 6cm of air.

Front 22

Properties of an beta radiation?

Back 22

An electron 0 -1 e
charge= -e
light and fast
moderately ionising
stopped by few mm of alminium

Front 23

Properties of a gamma radiation?

Back 23

short wavelength of Electromagnetic wave
charge=0
No mass and very fast
very weakly ionising
absorbed by thick lead or very thick concrete.

Front 24

Properties of a positron?

Back 24

beta+ 0+1e
charge +e
antiparticle of an electron. got the same relative mass but opposite relative charge.
reacts strongly with an electron to produce gamma rays.
Same properties as an electron.

Front 25

Properties of neutrion

Back 25

1 0 n
charge=0
does not interact much with matter
more penetrating than a & b and sometimes gamma
-be absorbed by nuclei of atoms in substances they pass through.
-indirectly ionising

Front 26

What is refraction?

Back 26

When radiation changes direction. this is caused by the change in density from one medium tot he other which changes speed of the radiation.

Front 27

What happens when a radiaton slows down

Back 27

It bends towards the normal. e.g when light enters glass or plastic it slows down.

Front 28

What happens if the wave hits a boundary at 90 degrees (e.g along the normal)

Back 28

It will not change direction but still slow down

Front 29

What happens when light hits another medium (e.g plastic and glass)

Back 29

Some of the light will pass through the medium but some will be reflected- it depends on the angle of incidence

Front 30

What are the two types of lens and their types

Back 30

Converging- convex
diverging-concave

Front 31

What does a converging lens do?

Back 31

they cause parallel rays of light to converge at the same focal point

Front 32

What does a diverging lens do?

Back 32

-They cause parallel rays of light to diverge at the same focal point.
-they focal point is the point where rays hitting the lens parallel to the principal axis appear to come from.
-they can be trace back until they appear to meet up at a point behind the lens.

Front 33

What is the focal length?

Back 33

The distance between the centre of the lens to its focal point.

Front 34

Where is the potential difference in the body

Back 34

Between the inside of the muscle cell and the outside

Front 35

What is the resting potential?

Back 35

When the potential difference across the cell membrane of a muscle cell is at rest.

Front 36

What can the PD be measured with?
What is the resting potential of a muscle cell?

Back 36

Very small needle electrodes.
The resting potential is about -70millivolts

Front 37

What is action potential? and how dos this affect the cell?

Back 37

-When a muscle cell is stimulated by an electrical signal and the potential difference increases from about -70mv to 40mv.
-the action potential passes down the length of the cell, making the muscle cell contract.

Front 38

What do electrocardiographs do?
how can accurate readings be obtained?

Back 38

-they measure the action potential of the heart using electrodes stuck on the arm, chest and legs.
-the patient should lie or sit still and relax

Front 39

What happens to the action potential when the heart beats?

Back 39

-When the heart beats an action potential passes through the atria making them contract and later another action potential pass through the ventricles, making them contract.
-once the action potential has passed through, the muscles relax.

Front 40

What do these action potential produce?

Back 40

They produce weak electrical signals on the skin.

Front 41

What is an electrocardiogram?

Back 41

The graph results that are displayed on a screen or printed out.

Front 42

What does a horizontal line show?
What does p show?
What does QRS show?
What does T

Back 42

-resting potential
-contraction of the atria
-the contraction of the ventricles and relaxation of the atria
-the relaxation of the ventricles

Front 43

What is the equation of the heart rate

Back 43

-freq.=1/time(sec)