photoelectric effect

Ek=hf-w

threhold frequency

w=h₀ f

higher intensity light, more ejected particles released

apply in phtovotalic cell

intensity of shineing light will increase the curreent but doest effect the kinetic energy.

work function is potential energy so it should be negative, since we adding energy to add it

gamma radiation has higher penetration

less ionizing power , to make the gamma radiation not easy to get absobed, it allow it to travell

split into 2 nuclei and more neutrons

chain reaction with the released neutron

modertor slow down the fast moving neutron to make it more likely get absober byu-235 nuclei

control rods abosrb the excessive neutron

fission products is unstable than product

density is portion to 1/R^3 (volume)portion to 1/A

M is portion to A

Ek rotation = 1/2 I w^2

Ek vibration =

w=dtheta/ dt

theta=w t

e: emf= electromotive force (voltage),

(potential difference- changing in potensial delta v)

volte = J/C joules per columb

potential at a point in the field: energy needed to move 1kg / 1C from infinity to a point in the field.

emf= -d(NBA cos (wt)) / dt

= wNBA Sin (wt)

B is also flux density, not only magentic field.

Q1: With fingers pointing in the direction of the magnetic field and thumb pointing in current direction through the projectile, the palm faces the direction of force on the projectile.

How it works:

A large current flows down one rail, through the conductive projectile, and back along the second rail

This current creates a strong magnetic field around each rail

The magnetic fields interact with the current in the projectile to produce a force.

The force accelerates the projectile along the rails and out of the gun at extremely high velocities

Q2: Electromagnetic induction is the process by which:

A changing magnetic field induces an electromotive force (EMF) in a conductor (Faraday's Law)

The induced EMF can drive a current if the circuit is closed

Q3:

1. inital speed

   • currents in the projectile that interact with the field to produce force

2. Self Acceleration:

   • The current through the rails creates a magnetic field perpendicular to the current in the projectile

   • Induction allows energy transfer without mechanical contact

   • The faster the current rises, the stronger the induced effects and acceleration

Switching off an electromagnet: A coil connected to the magnet experiences a current that tries to maintain the magnetic field.

right hand rules: FBI, thumb: force, field: finger, currrent: middle finger (for left hand)

sqaure root function

[because we move faster

: so we accelerate less per distance travelled

[ even though acceleration is constant

because we stay at that position for less ti

(660-680)/680=1/34

f=600x360/330=655

f1=fx (c /(c+v)=22/5

for moving source: delta lamda= v/c

expand thinking: the wavelength and speed of the light is effected by medium, if change in medium, the frequency of light won't change.

Explain how is this possible.

Hint: 1. What stays constant during refraction and what changes?

2. Think about topic E1 atomic physics and the cause of colour.

I radiated= I absorbed + I atmoshpere= 70+60= 130

phase diffdrent is the function moe horizontally shift, path different is the distance between two wavelnegth.

phase different= delta theta=2pai n

path difference = delta d= n lamda

It just needs electrons in the filament to start moving, bumping into atoms, releasing energy as heat and light.

The field sets this in motion almost instantly when the switch is closed.

R total = R1+ R battery

R battery = R ttoal- R1= 3.31-2.75= 0.56 om

real battety has internal resistence inside, the resistor need to be considered

ideal battery doesnn't has resistence, R total is just the resistor in the circut.

terminal potential= emf - IR

V=IR

s is displacement.

landing at same point measn displacement is the same relative to the inital point.

ut + 1/2 at^2 =ut + 1/2 at^2

t1=2. t2= 8

h=1/2 g t^2= 80

The resultant force(net force) is a single force that produces the same effect as the combined effects of multiple forces acting on an object

constant force, velocity might change, is net force = 0, then velocity doesnèt change

without friction:

a=f/m=mgsintheta/m=g sin theta

with friction

F=mg sin theta- miu mg cos theta

R=W+ma

the scale only shows the force that it give to human, w already include in the R

= mv-m(-u), right direction is possitive, remember to add negative to the u.

3. Momentum change in each direction

• Normal direction:

  Δpx=m(−vcos⁡θ）−m(vcos⁡θ)

• =−2mvcos⁡θ

• Tangential direction:

  Δpy=m(vsin⁡θ)−m(vsin⁡θ)=0

4. Resultant momentum change

∣Δp∣=root of [(Δpx)2+(Δpy)2]=2mvcos⁡θ

Answer: B — friction between the tyres and the road.

• The centripetal force always points towards the centre of the circle.

• The displacement at any instant is along the tangent to the circle (same direction as velocity).

• That means force ⟂ displacement at every instant.

2. Work definition

dW=F⋅ds=F dscos⁡θ

Here θ=90∘(because force is perpendicular to displacement), so

dW=0

Over one revolution
Integrating over the entire circle doesn’t change anything — force and displacement are always perpendicular ⇒ total work = 0.

3/2kT=average kinetic energy per molecule\

Latent heats (fusion vs vaporization):

• Fusion (solid → liquid): requires breaking some intermolecular bonds so molecules can move past each other, but they remain close.

• Vaporization (liquid → gas): requires breaking all intermolecular bonds so molecules are far apart.

• Thus, latent heat of vaporization ≫ latent heat of fusion.

• So statement I is false.

Specific heat capacities (solid vs liquid):

• In solids, molecules are bound in a lattice, vibrations absorb heat, but degrees of freedom are limited.

• In liquids, molecules move more freely → more modes of energy storage → generally higher heat capacity.

• So statement II is true.

• Freezing = liquid → solid.

• Molecules go from disordered (liquid) to more ordered (solid).

• Entropy of the water molecules decreases.

Second Law of Thermodynamics: in any real process, entropy of the universe must increase.

• A refrigerator removes heat from inside and releases even more heat to its surroundings (because it also dumps the work input from the motor as heat).

• If the fridge door is left open, the “inside” is just part of the same room.

• Net effect: the fridge adds more heat to the room than it removes.

So:

• The room’s temperature increases over time.

Step 2. Entropy change of the room’s air

• Added heat increases molecular disorder.

• Entropy of the air in the room increases.

✅

wavelength= 2L/n

boundary condition

string

2 closed end

sound

2 cosed, 2 open

wavelength=4L/n. (n can only be odd number)

string and sound:

1 open 1 closed ending.

L is the length from 1 end to another end

6: the momentum is always conserved, but the kinetic energy is not conserved in inelastic system

15-19cm, 2-3kg, k=f/x=10/0.04=250.

x=f/k=(5-2)/250=0.12

0.12+0.15=0.27m

Clockwise moment=Anticlockwise moment

Torque (moment) depends on force × distance from pivot.

20x 0.6+20x 0.9=30

30=Tx0.5

T=60

• III depends on mass and geometry, not on velocity.

II. Angular velocity proportional to linear velocity.

• No slip condition:

  ​

• So ω∝v

III. Angular acceleration is zero.

• Because the cylinder rolls at constant velocity → no angular acceleration.

We already calculated:

ω=2πf=10π rad/s

Q2. Angular acceleration of the fan

α=Δω/Δt

Q3. Angle rotated in 10 s

Use rotational kinematics:

θ=ω0t+1/2αt^2

So:

• Lower temperature

• Higher luminosity (because it compensates for being further away).

Not quantisation (discrete energy levels, but here the key word is matching frequencies).

This is resonance: absorption occurs when the driving frequency = natural frequency.

P=V^2R/P

So energy (heat) in time t:

E=Pt=V^2R/P x t

Step 3: Substitute values

We need to apply the First Law of Thermodynamics:

ΔU=Q−W

where:

• ΔU\Delta UΔU = change in internal energy

• Q = heat supplied to the system

• W = work done by the system

• delta u= 6-2=4

Incident angle must be greater than the critical angle.

B. Superposition of waves.

C. Vector analysis of waves.

D. Total internal effect of waves

B

Opposite directions, same wavelength

Distance between consecutive nodes

In a standing wave, node → antinode = ¼λ,

so node → node = ½λ.

Q3. Antinode definition

Antinode = maximum displacement (amplitude largest).

Answer: C. Amplitude detected will be at a maximum

𝑟

f

r

​

.

q10, one north pole one south pole attract

at q is p to q , fleming right hnad rule

• When air is compressed, the gas molecules have less accessible volume.

• That means lower entropy for the gas inside the tyre.

So: entropy of air pumped in decreases.

Step 2. What about the surroundings (the pump + environment)?

• Compression is not reversible, some energy is lost as heat to surroundings.

• That heat increases the entropy of surroundings.

• The increase is equal or larger than the decrease inside the tyre (because total entropy must not decrease, by the second law of thermodynamics).

A very wide central maximum.

Central maximum is much brighter and wider than the others.

Successive side fringes (minima/maxima) have rapidly decreasing intensity.

• Increasing b (slit wider) ⇒ sin⁡θbecomes smaller ⇒ the diffraction minima move closer to the center.

• This makes the envelope narrower, i.e. peaks are more closely spaced.

• The maximum intensity of the envelope also increases because a wider slit lets through more light (larger area).

So:

• I. wavelength → Yes

• II. wave speed → No (always c in vacuum)

• III. frequency → Yes

λ) → distance in space between two crests (or any repeating points). Unit: metres (m).

Period (T) → time in seconds for one full wave cycle to pass a point. Unit: seconds (s).

They’re linked through the wave speed:

𝑣=𝜆/𝑇=𝑓𝜆

act like a projectile motion explain by energy conservation

the extra force is being applied on the particles, the strength between the plate, the kinetic energy need to be smaller the keep the balance.

x′=γ(x−βct),

ct′=γ(ct−βx),ct'

γ=1/root of 1-β^2=1.67

x=1, ct=0,

x'=5/3

ct'=-4/3

rocket: l'=l/gama=14.4ly

t'=l'/v=18 years

delta t=gama times dellta t0

(change in time)

lorentz transformation

t- coordinates

(actual clock measument at that perticular time)

v=c/ tan60= 0.577c

question 42+and - 2

absolute value= (log 44- log 40) /2

y: electron degeneracy pressure

or total displacment is 0

w=fs