Y1 Past Paper Corrections Flashcards
Key terminology with waves
- Use the term ‘oscillations’
Relationship between wave intensity and amplitude
I ∝ A^2
Wavelength definition
The minimum distance between two adjacent points oscillating in phase, e.g. distance between two peaks/compressions.
State the principle of superposition
When two or more waves meet at a point, the resultant displacement at that point is equal to the sum of the displacements of the individual waves.
What happens to fringe separation if distance slits in double-slit experiment increases?
λ = ax / D
a = distance between slits
x = fringe separation
D = slits to screen distance
- D is constant, λ is constant
- If a increases, X decreases.
Show W = VQ can be written in base untis
V = W/Q
W = N x D
W = kg ms-2 x D
Q = As
now divide the top by buttom
SI units
- metre (m)
- kilogram (kg)
- second (s)
- ampere (A)
- kelvin (K)
- mole (mol),
prefixes below 10^1 metres
deci -1
centi -2
milli -3
pico -12
femto -15
Units expressed in other SI units
N = kg ms-2
Pa = Nm-2
J = Nm
W = J s-1
V = J C-1
Ohm = V A-1
C = A s
Hz = s-1
Remember for calculating voltage/resistance when 2 components are invovled
V1 / V2 = R1 / R2
How to measure diameter
- Vernier callipers, repeat measurements ALONG object.
Why is it useful to make sure metal contacts used to complete a circuit are large?
To ensure the entire CSA of the conductor is in contact with the contacts.
Formula to calculate cross sectional area, and device
- Use a micrometre in multiple places, take average if needed, then πd^2 / 4
Practical to find breaking stress of wire
- Method of fixing wire and load at other end.
- Safety (eyes and floor with sand).
- Measure masses.
- Measure diameter (micrometre), take average, repeat.
- Calculate force mg, and CSA
- Breaking stress = max force / CSA
Practical to find Young’s Modulus of wire
- Method of fixing wire and load at other end.
- Safety (eyes and floor with sand).
- Measure masses.
- Measure diameter (micrometre), take average, repeat.
- Calculate force mg, and CSA
- Graph mg/N against e/M, gradient = e/mg
- Young’s modulus = mgL / Ae, now L / A x Gradient
Stress/strain graph for loading/unloading on glass and rubber
- Glass is a straight line through the origin
- Rubber extension starts slow, then gets much larger, then slows. Gradient high, flattens, high.
Formula to find speed of electron in electron gun
eV = 1/2 mv^2
v = √(2eV / m)
Relationship between de broglie wavelength and p.d
λ ∝ 1 / √V
If p.d increases de Broglie wavelength decreases, pattern becomes smaller.
de Broglie wavelength formulas
λ = h / p
v = √(2eV / m)
Explain why a ball falling from rest follows the conservation of momentum
The earth is part of the closed system. The earth has opposite momentum to falling ball, and moves upward. Albeit by a tiny speed, as its mass is so large.
Define Interference
The superposition of coherent waves. The waves can superpose constructively or destructively.
Relationship between resistance per unit length of wire r, and diameter D
r = 1/D^2
What is refractive index
Speed of light in vacuum / speed of light in material
How is momentum related to KE
p= √(2m x KE)
relationship between KE and momentum
KE = p^2 / 2m
Snell’s Law
The ratio of the sine of the angle of incidence to the sine of the angle of refraction is a constant.
n1 sinθ1 = n2 sinθ2
Formula relating power, force, velocity
P = Fv
Impulse formula using force and time
Impulse = F x Change In Time
Phase difference to path difference CORRECT
Phase Difference = 2pi x path difference / lambda
Wavelength for radiowaves
> 10^6 to 10^-1 (metres)
Wavelength for microwaves
10^-1 to 10^-3
Wavelength for infrared waves
10^-3 to 7x10^-7
Wavelength for visible light
700nm 400nm
Wavelength for ultraviolet
4x10^-7 to 10^-8
Wavelength for x-rays
10^-8 to 10^-10
Wavelength for gamma rays
10^-13 to <10^-16
Possible wavelength for gamma and X-ray overlap
10^-10 to 10^-13
For a wire, formula related to spring stiffness and the wire’s properties
K = YA/L
stiffness = young’s modulus x CSA / length
Volume of sphere
4/3 * π * r^3
Relationships between intensity and distance
I ∝ 1/d^2 (intensity inversely proportional to distance squared)
d ∝ 1 / √ I (distance inversely proportional to root intensity)
Phase Difference Definition
- Difference in degrees between the same point on two waves
Formula relating the power, number of photons emitted, and energy of a single photon
P = N × E
E = λ / hc n
