PHYSICS

Question 1

Explain what is meant by coherence

Answer 1

Constant phase difference

Question 2

Describe the diffraction of monochromatic light a sit passes through a diffraction grating.

Answer 2

Wave pass through gaps/slits spread into geometric shadow

Question 3

Describe how the principle of superposition is used to explain white light at zero order.

Answer 3

Each wavelength travels the same path or are in phase displacement add to give resultant displacement

Question 4

I=Q/T=nAvq

Answer 4

N-number density
A-横截面积
v-mean drift velocity of electric carrier
q-charge of electric carrier

Question 5

V=W/Q

Answer 5

p.d.=energy transferred (or work done) divided by charge
Also, W=QV
W-work done in J
Q-total charge in C
V-potential difference in V

Question 6

Relationship between resistivity and temperature of metal

Answer 6

Resistivity increases as temperature increases.
Reason: more collisions causes more energy transferred into heat energy, and it impedes the path of free moving electrons

Question 7

The relationship between resistivity and temperature of semiconductor.

Answer 7

Resistivity decreases as temperature increases.

Reason: as temperature increases, more electrons are delocalized so that more charge carriers are to move freely.

Question 8

I-V graph of filament lamp

Answer 8

┌(;￣◇￣)┘upside down

Question 9

I-V graph of semiconductor diode

Answer 9

正向导通反向截止（反向电阻无穷大）

Semiconductor diode is a component which allows electric current in only one direction.

Question 10

Explain why an interference pattern is observed on the screen

Answer 10

1. Waves from the double slit are coherent
2. Waves from each slit superimpose/overlap
3. Maximum/bright fringes where path difference=n x wavelength or phase difference= n x 360 degree

Question 11

Resistivity formula

Answer 11

R=p(L/A)

Question 12

Resistance against temperature graph for NTC thermistor

Answer 12

y=x^(-1) 正x轴

Question 13

LDR

Resistance against light intensity graph

Answer 13

Light-dependent resistor (LDR)

Question 14

Potentiometer circuit

Answer 14

Measure unknown electromotive force

Question 15

1V

Answer 15

1J/C

Question 16

e.m.f.

Answer 16

E=W/Q

Energy transformed per unit charge

Question 17

p.d.

Answer 17

V=W/Q

Energy transformed from electrical to other forms per unit charge

Question 18

Internal resistance equation

Answer 18

e.m.f. =terminal p.d. +lost volts
E=V+Ir=I(r+R)
I=E/(r+R)

Question 19

Condition of ohm’s law

Answer 19

Constant temperature

Question 20

Resistivity formula

Answer 20

R=p(L/A)

Question 21

Resistance against temperature graph for NTC thermistor

Answer 21

y=x^(-1) 正x轴

Question 22

LDR

Resistance against light intensity graph

Answer 22

Light-dependent resistor (LDR)

Question 23

Potentiometer circuit

Answer 23

Measure unknown electromotive force

Question 24

1V

Answer 24

1J/C

Question 25

e.m.f.

Answer 25

E=W/Q

Energy transformed per unit charge

Question 26

p.d.

Answer 26

V=W/Q

Energy transformed from electrical to other forms per unit charge

Question 27

Internal resistance equation

Answer 27

e.m.f. =terminal p.d. +lost volts
E=V+Ir=I(r+R)
I=E/(r+R)

Question 28

Threshold voltage

Answer 28

The voltage reached when semiconductor diode starts to conduct

Question 29

Filament lamp

Answer 29

Not ohm component

except when the voltage or current is very small

Question 30

Thermal resistor/ thermistor

Answer 30

NTC-negative coefficient 正比例函数一三象限

PTC-positive coefficient

Question 31

R的各种正比关系

Answer 31

R direct proportional to L
R direct proportional to I/A
R direct proportional to L/A
R direct proportional to pl/A