ep:The mass on the spring reciprocates up and down.

displacement 位移（从平衡位置的距离）

ep:If the equilibrium position of a spring is x=0, and at a certain moment the block is at x=+0.10m, then the displacement is +0.10 m.

frequency 频率（每秒的震动此事）

If an object vibrates up and down 2 times per second, its frequency is f=2Hz.

period 周期（完成一次震荡所用的时间）

If a pendulum clock takes 2 seconds to swing from left to right and back to left, then its period is T=2s.

total energy 总能量（SHM中恒定）

A block with a mass of 0.2 kg and an amplitude of 0.05 m has an angular frequency of w=10rad/s

ET=1/2*0.2*10^2*0.05^2=0.25J

This is the total mechanical energy that remains constant throughout its simple harmonic motion.

potential energy 势能

Simple Harmonic Oscillators：✅

Damped Harmonic Oscillators：❌

(not only the consrvative forces.There is friction摩擦力)

b. Dissipative forces?(耗散力)

Simple Harmonic Oscillators：❌

Damped Harmonic Oscillators：✅

(There are dissipative forces (such as air resistance and friction))

c. Time-dependent amplitude?（幅度随着时间变化）

Simple Harmonic Oscillators：❌

Damped Harmonic Oscillators：❌

(Floating constant and decaying over time)

d. Form of potential energy function.

Simple Harmonic Oscillators：U=1/2 kx^2

Damped Harmonic Oscillators：the total energy will be less

f. Energy loss over time

Simple Harmonic Oscillators：❌

Damped Harmonic Oscillators：✅

(the reason that damped harmonic oscillators energy loss over time,conect with b)

g. Graph of displacement vs time.

Simple Harmonic Oscillators：cos/sin

Damped Harmonic Oscillators：get more lower sin/cos

h. Equation of motion.

Simple Harmonic Oscillators：ma + kx = 0

Damped Harmonic Oscillators：ma + bv + kx = 0, where b is the damping coefficient

i real world example

Simple Harmonic Oscillators：Pendulum clock

Damped Harmonic Oscillators：Shock absorber

vocabulary:

damping减震

criticall damping 临界减震

light sampling 轻减震

heavy sampling 重减震

Destructive out phase

Reflection at the boundaries then constructive and destructive interference forms nodes and antinodes for specific frequency

• Be testable by changing one variable and measuring another (like a real experiment)

• Be focused on physics concepts (waves, resonance, standing waves, frequency, amplitude, damping, etc.)

• Show curiosity! It’s okay if you’re not sure how you’d do it yet — we’ll develop the ideas in class.

• How does changing the frequency of the vibrator affect the number of standing wave loops formed on the string?

Task 2 - Add a reflection called 'Standing Wave Equipment Exploration July 31st' to the IA Skills part of your PADLET.

• What equipment did you find most interesting today? Why?

• I found the vibrator and string system most interesting. Watching the string form clear standing wave patterns as the frequency changed was really engaging.

• 
  

• What was one thing you found confusing or surprising?

• I was surprised by how specific the frequencies had to be for standing waves to appear. If the vibrator was even slightly off, the wave pattern would collapse. 

• 
  

• Which of your personal research questions would you most like to test? Why?

• How does the height of water in a bottle affect the frequency of sound produced when the bottle is tapped?(ia)

Example Research Questions

These are just examples to inspire you — don’t copy them!

• How does the tension in a string affect the frequency of its first harmonic?

• What is the effect of changing the liquid in a resonance tube on the resonant frequency?

• How does damping affect the clarity of standing wave patterns on a string?

Rays =drection of the wave

🙅Frequency is set by the source and stays constant across boundaries.

🙆(change)Since speed changes and frequency stays the same, wavelength must change: v=fλ

🙅Colour depends on frequency, so if frequency doesn’t change, the perceived colour stays the same.

🙅Energy of a photon is E=hf, so if frequency stays the same, energy stays the same.

🙅Still the same type of EM wave (e.g., visible light stays visible).

First dark pattern condition第一暗纹条件

asin=入

proportional priority method

W1/W2=L1/L2

Get d using a fixed angle and wavelength

另一个角度对应的波长，把角带 入=dsinθ

The wavelength corresponding to another angle, substituting the angle into = dsinθ

*2:its means both side of the graph

+1 its means the central maximum, which n=0

光程差 ΔΔ 指两束光从不同路径到达同一点时，它们实际传播的距离之差。光程差决定两束光到达时的相位差，从而决定它们是相长干涉（增强）还是相消干涉（抵消）。

Integer multiples of λ bright

Half multiples of λ dark

Single slit: Integer multiples of λ across the slit dark

Bright fringes appear between dark fringes

Remember to check at the end sinθ≤1

Otherwise, that level does not exist.

Double slit/grating:整倍数λ 就是亮

半倍数λ 就是暗

Single slit:整倍数  暗

亮纹在暗纹之间出现

slide 3:diffraction grating N slits

principal vs. secondary maxima

N-1 minima

N-2 secondary maxima

(i) you are stationary AND the ambulance is stationary.

The sound heard /the same as the original siren, no change.

(ii) you are stationary AND the ambulance is moving away from you.

Sound you hear/The pitch is lower (the frequency is lower), and the sound sounds "deeper"

(iri) you are stationary AND the ambulance is moving towards you.

Sound you hear / The pitch of the sound increases (the frequency becomes higher), and the sound sounds "sharper".

(iv) you moving towards a stationary ambulance.

The sound you hear / the pitch is rising because you are actively "moving towards the source of the wave".

(v) you are moving away from a stationary ambulance.

The sound you hear /the pitch is lower because you are “moving further” away from the source of the wave.

component of relve

paralle (to the ine sight)

after this we get T1=2pai square root m/k (T)*1/2, also T1=T*1/2

so the answer is 0.5

after this we get T1=2pai square root m/k (T)*1/2, also T1=T*1/2

so the answer is 0.5

but D have additional force,the bounce of the basketball when it hits the floor

Ep=Extra energy（such as high）

the doppler effect will included

frequency

wavelength

(color&energy)

BUT the wave speed will not change(cause the speed of light in vacuum is c = 3.0 × 10^8 m/s)

and for the wavelength will decrease when it moves towards to me ,and when it moves away from me it will increase.

who's moving

so the question said that the observer is STANDING STILL, and a fire engine is APPROACHING at high speed.

so the fire engine is moving, so used the moving source equation.

answer is D

The light waves are stretched → their wavelength increases → and they shift toward the red end (red shift).

If a galaxy moves toward us:

The light waves are compressed → their wavelength decreases → and they shift toward the blue end (blue shift).

so the answer is A

so when the speed is increase the kinetic energy increase

potential energy is the energy which connect with the displacement when displacement increase the potential energy will increase

so in SHM

at balance point x=0

⬆️speed /kinetic energy

⬇️potential energy

amplitude position振幅

speed=0

kinetic energy=0

⬆️potential energy

longitudinal wave&transverse wave

"Perpendicular to each other

Perpendicular to the direction of wave travel → making EM waves transverse."

so we can know that electromagnetic wave is a transverse wave

No medium needed

Travel speed: In a vacuum, they move at the speed of light, c ≈ 3.0 × 10⁸ m/s.(this one is on the data booklet)

40,000nm=4.0×10−5m

70,000nm=7.0×10−5m

LOOK AT YOUR DATA BOOKLET

so its longitudinal wave choose b

II is not correct cause the graph shows that the period is 3

III is not correct because if you use II data then calculate it you will find out that is wrong.

because the moving source is away from the observer, so it should be -.

B: ΔL = 0.062 m, λ = 0.062 m, d = 0.05 m→ ΔL/λ=1, so it’s a first-order maximum. Fits perfectly. ✅

C: ΔL = 2.424 m, λ = 1.212 m, d = 0.10 m → Completely wrong.

D: ΔL = 0.031 m, λ = 0.031 m, d = 0.10 m → Path difference is calculated incorrectly.

w=入D/S

Marks cheme

• [1] States total internal reflection (TIR) at the water-air boundary.

• [1] Explains condition: water has higher n than air and incidence angle exceeds

1. my answer for this queastion

because the laser shoot in the water, and the laser beam stays inside carred of water ,cause light have in caecum is 3.00*10^8 ms^-1 but in water ,we have different density to affect the light speed to affect the light speed ,so if i need to control it in ceacum system, laser beam need to stays inside the curved stream of water.

2. what should i write

TIR/critical angle

this question is about TIR and different refractive indices cause changes in the speed of light

3. rewrite the answer

The laser beam stays inside the curved stream of water because total internal reflection occurs at the water–air boundary. Since water has a higher refractive index than air, and the incidence angle is greater than the critical angle, the light is totally internally reflected and follows the curve of the water stream.

(b) calculate the speed that the laser beam travels inside the curve steam of water.

v=c/n

=3.00*10^-8/1.33

=2.26*10^-8

(c) determine whether the laser beam can or cannot travel inside the curved stream of water when the angle of incidence is 55(angle)

Marks cheme

Decide if a 55° ray is guided (2 marks)

• [1] Computes critical angle: sine_c = n_air /n_water = 1.00/1.33 → 0_c =48.8°

• [1] Since 55° > 0- -c, TIR occurs → the beam remains inside the water.

1.what should i write

Calculate critical angle

Since 55∘>48.8∘55∘>48.8∘, total internal reflection occurs.
Therefore, the laser beam remains inside the water stream (guided).

⚠️ please be clear that what the question about

(ii) the laser is changed from green to red

marks cheme

• [1] Change colour green→red: n slightly smaller for longer ^ → bends less (refracted angle in water slightly larger).

what should i write for this question

Water has a slightly lower refractive index for red light than for green light

Because water’s refractive index is slightly lower for red light, the critical angle is slightly larger, but 55° is still above the critical angle, so total internal reflection still occurs and the red laser stays inside the water.

(iii)the stream flows inside a glass tube instead of air

marks cheme

• [1] Water inside a glass tube (n_glass > n_water): no TIR at water-glass → lig refracts into glass; confinement in water lost.

what should i write

Because water’s refractive index is slightly lower for red light, the critical angle is slightly larger, but 55° is still above the critical angle, so total internal reflection still occurs and the red laser stays inside the water.

(a)(i) Radial speed from Ha shift (2 marks)

• [1] Uses v = с(▶️入/入) with ▶️入 = (656.0 - 656.2) nm → ▶️入/入 = -3.05×10-4.

• [1] v ~ -9.2×10* m s-4; negative sign (blueshift) indicates motion towards Earth.

⚠️ read the question and understand the question

Δλ/λlab=v/c

so we can get v=Δλ/λlab

|Δλ|/λlab=0.2/656.2=3.049*10^-4

so

|v|=3.00*10^-8*3.049*10^-4

=9.15*10^-4

Estimate the angular position of the third minimum for this interference pattem.

0-=2.5*10^-2rad from the centre

Calculate the grating spacing d.

1.31*10^-5

Determine the number of slits N inside the grating.

36

L=入/2

入=2L*0.45=0.90m

speed of wave

v=f入

160=f*0.90

so we can know the frequency is 160/0.90

f=178hz

The small metal spheres move inside the empty spaces when the frame vibrates.
They collide with the walls of the cavities, and energy is transferred to heat and sound.
This dissipates the mechanical energy of the frame, so the oscillations are damped.
As a result, the amplitude of vibration decreases with time, as shown in the graph.

one common physical set up here is that d receives sound by two routes the direct ray L to D(length=0.70) and the ray that goes L to P then reflects at the water surface and travels P to D(total lengthLP+PD)

Δs=(LP+PD)−LD=1.00−0.70=0.30 m.

Δs=0.30 m=1.5λ=(1+1/2​)

Mass defect: mass difference between separate nucleons and bound nucleus.

(ii) Use error propagation (in data booklet)

(iii) calculate the uncertainty in repeated measurements.

so Q=N*mgl*s

Q=(nm)c▶️T

Latent heat (phase change):Q=mL

Freezing (liquid to solid)  use Q=mLf

Sloping sections: temperature decreases to sensible heat change

gas to liquid

Cshc JKg^-1K^-1

Q=mc▶️T

c=Q/m▶️T

solar intensity recived by earth

whole surface=4 pai r^2

disk(circle)=pai r^2

incoming radiated power (from the sun)

=

outgoing radiation power(from the earth)

incoming intensity:100(Wm^-2)

use the formula : 0.30*100=30

100-30=70

70+60=130

answer:D

so for double slit it have bright inference fringes(light intensity increase and V increase ) and dark inference fringes(light intensity decrease and V decrease )

because this question says the train will move in a same speed ,because when the laser bean passes through a double slite ,the light waves exiting. the two slit different and superimpose forming interference fringes in space.

• Time delay = 4.0 ms4.0 ms 1 mark

• Phase difference

• δ=(4.0/16.0×360∘)=90∘

• or δ=(π2) rad

A standing wave is formed when two waves of equal frequency and amplitude travel in opposite directions and interfere

• Purpose: Measure potential difference between two points.

• Ideal Resistance:
  ∞ (infinite resistance)

• Reason:
  An ideal voltmeter should draw no current from the circuit.
  Infinite resistance ensures current through the voltmeter is zero, so it does not affect the circuit it is measuring.

non-ideal voltmeter

• Real Resistance:
  Very high, but finite (e.g., megaohms).

• Reason:
  A non-ideal voltmeter still draws a tiny amount of current, which can slightly affect the circuit and cause measurement errors, especially in high-resistance circuits.

For example, when a satellite 🛰️ orbits the Earth 🌍 there is a centripetal force which is due to the gravitational force between the Earth and Satellite.

vernier caliper

exhibiting a clear order (low entropy).

After stirring: Milk and coffee are evenly mixed

with a more random molecular distribution (high entropy).

Irreversible!!!!!

micro states

• Isobaric process (constant pressure)

  • On a P ⁣− ⁣VP−V graph, constant pressure means PP does not change.

  • So the line is horizontal (volume changes, pressure stays the same).

• Isochoric process (constant volume)

  • Volume is fixed, so on a P ⁣− ⁣VP−V graph it is a vertical line (pressure can change, volume does not).

• Isothermal process (constant temperature)

  • For an ideal gas: PV=nRT=constantPV=nRT=constant at fixed TT.

  • This gives a hyperbola: as VV increases, PP falls smoothly such that P∝1VP∝V1​.

• Adiabatic process (no heat exchange, Q=0Q=0)

  • For an ideal gas: PVγ=constantPVγ=constant with γ>1γ>1.

  • So pressure drops faster with increasing volume than in the isothermal, giving a steeper curve.

Positive charge: The direction of the force is the same as the electric field lines (moving towards lower potential along the electric field lines).

Negative charge: The direction of the force is opposite to the electric field lines (moving towards higher potential against the electric field lines).

this is because there is a strong nuclear force(strong force in short distance)

as i mention before in a atomic nucleus, it contains protons and neutrons, but if the number of protons is increase the number of neutrons also needs to increase, to make it more stable.

two atom in high temperature and high press turn into one big atomic nucleus and release more energy during the process.

fission:

chain reaction) :split to 2 atomic nucleus, then split to more atomic nucleus.