PPQ Corrections

Question 1

The peak wavelength of radiation is _______ for hotter objects.

Answer 1

shorter

Question 2

The rate of radiation emitted is _______ for hotter objects.

Answer 2

greater

Question 3

What does the graph that shows the relationship between frequency and wavelength of photons of radiation look like?

Answer 3

standard curve with negative gradient

Question 4

What happens to the speed and the wavelength of a ray of light when it goes from water to air?

Answer 4

Both increase

Question 5

Tension = …

Answer 5

Force + FRICTION

Question 6

What happens to the tension when friction is increased?

Answer 6

Tension increases.
Unbalanced force remains the same.

Question 7

What do airbags do?

Answer 7

Increase the time of contact the driver has with the steering wheel.
This reduces the force experienced by the driver.

Question 8

A light will only turn on when the pn junction is _______ bias.

Answer 8

forward

Question 9

What’s the difference between photons emitted by blue LED and photons emitted by red LED?

Answer 9

Blue has a larger band gap.
Photons of blue light have more energy.
Photons emitted by blue light have a shorter wavelength.

Question 10

What is the fundamental force associated with beta decay.

Answer 10

Weak nuclear force.

Question 11

Why is alternating voltage used in the cyclotron.

Answer 11

To ensure the electric field is always in the correct direction.

Question 12

Hand trick:

Answer 12

Thumb: Current
Pointer: Magnetic field
Middle: Force (out of page)

Question 13

Explain how a line emission spectrum is produced:

Answer 13

If an electron is in an excited state it can return to a lower energy level. When it does this, it emits a photon.
Different transitions produce different lines (frequencies of photons).

Question 14

Why are some lines on the emission spectrum brighter than others?

Answer 14

More electrons are making those transitions per second.
Therefore, there are more photons of that specific energy emitted and produce brighter lines.

Question 15

What is a critical angle?

Answer 15

The angle of incidence that produces an angle of refraction of 90°.

Question 16

What effect does increasing total resistance have on the power dissipated by internal resistance?

Answer 16

Increasing total resistance decreases power dissipated by internal resistance.
This is due to the current being decreased by increased resistance.

Question 17

Absolute uncertainty

Answer 17

Take the highest % uncertainty of products.
Times that by the answer.

Question 18

Suggest an improvement to any experiment…

Answer 18

Repeat the measurements and take the mean.

Question 19

Force parallel to the slope

Answer 19

mgsinθ

Question 20

Fermions

Answer 20

Family of particles made up of quarks and leptons

Question 21

The two types of quark are

Answer 21

Baryons (3 quarks)
Mesons (quark and antiquark)

Question 22

Leptons consist of

Answer 22

Electron
Muon
Tau
Neutrinos

Question 23

Hadrons

Answer 23

Held together by the strong force
E.g baryons and mesons

Question 24

As a capacitor charges the current…

Answer 24

Decreases

Question 25

Potential difference across a resistor _________ as capacitor charges

Answer 25

Decreases

Question 26

What effect does reducing velocity have on the maximum height reached?

Answer 26

Reducing velocity reduces the INITIAL VERTICAL VELOCITY decreasing the maximum height reached.

Question 27

Interaction is elastic when...

Answer 27

TOTAL Ek before = TOTAL Ek after

Question 28

Photovoltaic Effect

Answer 28

When photons of light are incident on a photodiode (e.g pn junctions) it produces a potential difference.

Question 29

How is a potential difference produced when photons of light are incident on a photodiode?

Answer 29

Photons hit pn junction which moves electrons up into conduction band removing the depletion layer, causing a current.

Question 30

Why are protons accelerated in an electric field?

Answer 30

Protons are positively charged. Protons experience a force in the electric field.

Question 31

What happens to the speed of a proton in an electric field when the distance it travels is increased?

Answer 31

No effect since work done is the same.

Question 32

Why would a setup not be suitable for investigating inverse square law?

Answer 32

Setup is not a point source.

Question 33

Define the term 'coherent'

Answer 33

Waves have a constant phase relationship.

Question 34

What is emf?

Answer 34

The energy gained by 1 coulomb of charge passing through the battery.

Question 35

E=IR+Ir can be rewritten as...

Answer 35

emf = t.p.d + lost volts

Question 36

When asked how to take emf reading from a setup say...

Answer 36

Reading on the voltmeter before the switch is closed.

Question 37

What is conserved in an elastic collision?

Answer 37

Total momentum Total energy Total kinetic energy

Question 38

What happens to the wavelength on the screen when timebase is halved.

Answer 38

It is doubled.

Question 39

System uncertainties occur when...

Answer 39

Measurements are either all smaller or all larger than the true value of the quantity.

Question 40

How does quartering mass affect the gravitational force of attraction?

Answer 40

Quarters it.

Question 41

How does halving the distance between objects affect the gravitational force of attraction?

Answer 41

Makes it 4x larger.

Question 42

Vertical tension(Tv)=

Answer 42

Tcosθ

Question 43

What happens to tension when angle is increased.

Answer 43

Decreases since the cosine of the angle decreases.

Question 44

When adding a line to a graph showing how energy emitted per second varies with wavelength for a HOTTER star

Answer 44

Make sure the line is always above the cooler stars line.

Question 45

Describe how apparatus can be used to verify inverse square law.

Answer 45

Obtain values of irradiance for different distances. Determine I × d^2 Values of Id^2 should be constant.

Question 46

Why does light with a shorter wavelength produce a smaller angle between central and first maxima?

Answer 46

The path difference is smaller therefore the spots are closer together.

Question 47

What effect does the slit separation have on the angle between central and first maxima?

Answer 47

Larger slit separation produces a smaller angle which is more difficult to measure.

Question 48

Greater refractive index causes ____ internal reflection.

Answer 48

more

Question 49

Why does voltage decrease when a circuit with a resistor is connected.

Answer 49

When the circuit connects a current flows through it causing volts to be lost across the resistor.

Question 50

When a lift accelerates downwards the reading on the scale will be

Answer 50

A CONSTANT value less than the true weight.

Question 51

Name the 6 quark types

Answer 51

up/down top/bottom charm/strange

Question 52

The right hand rule is only for...

Answer 52

Negative particles

Question 53

What happens to the frequency of a ray of light when it goes from air to water?

Answer 53

Remains unchanged.

Question 54

What effect does reducing irradiance have on the kinetic energy of the photoelectrons ejected from the metal?

Answer 54

No change since irradiance does not affect the energy of the photons.

Question 55

Explain why the photoelectric effect provides evidence for the particle nature of light.

Answer 55

Each photon removes one electron.

Question 56

Total internal reflection occurs when...

Answer 56

The angle of incidence is greater than the critical angle.

Question 57

A prism with a lower refractive index will have...

Answer 57

A spectrum with less dispersion.

Question 58

2 features of the Bohr model:

Answer 58

A positively charged nucleus. Electrons in shells orbiting the nucleus.