Modern phy - 1 Flashcards
wht is quantum theory
- lightt is made up of small particles called phsoton
- light travels in groups of photo called packet of energy
energy of photos
E = hnew = hc/ lemda
h - plancks 6.62 10^ -34
c - speed of light
new - frequency of photon
lemda - wavelength of photon
- rest mass of photon?
- KE =
3.1 ev = - energy mass roatation formula, given by?
- momentum of photon?
- rest mass of photon is zero as it never stays at rest
- KE = qV
3.1 ev = 1.6 10^ -19 - E =mc^ 2
- p = h / lemda
p = E/ c
intensity of photons?
I = energy/ area * time
energy of photons?
E = Nhnew
n = N/t [ no. of photons per sec]
n’ = N/a*t [no. of phtons per sec and per unit area]
power of photons?
P = ENERGY / TIME
P = Nhv / t
P = nhc / lemda
relation bw power and intensity ?
P = IA
no. of photons per sec?
n = p lemda / hc
n = 5 * 10^24 P lemda
radiation pressure ? reflecting and absorbing 4 points each
pg 3 in notes
when surface is partially absorbing and partially reflecting, f =
F = Pi + Pr / c
Pi - incident power
Pr - reflected power
if frequency doesn’t chnage then intensity?
intensity of photon depends on n
wht is electron emmission
ejecting of elecrons from metal surface
types of electron emmission and define them
- thermioninc emmission - electron is emitted from thermal energy
- field emission - electron is emitted from strong electric field 10^8 v/m
- photoelectric effect - emission of electron with help of light
wht is photoelectric effect PEE?
-emission of electron
- when sufficient energy [light]
- is incident on metallic surface
- these electrons are called photoelectrons and current generated due to these electrons is called phto current
- effect discovered by HERTZ
- law given by LENARD
- ecplained by EINSTEIN asumming light is made up of photon
threshold frequency ?
- minimum frequency of light [incident phtons]
- due to which electrons can emit
threshold wavelength ?
- max wavelength of light [incident phtons]
- due to which electrons can emit
work function ?
- min enegy required
- for electron to emit from metal surface
- it depends on metal only[ [2 ptk]
- 2 formulae notes pg 7,8
photosensitive plate made up of?
metallic [Cs]
- KEmax =
- KEmin =
- photocurrent =
- stopping potential [Vs] =
- saturation photocurrent =
- KEmax = outer layer electron
- KEmin = 0
- photocurrent = I = ne/t
- stopping potential = negative potential of anode
- wrt to cathode
-is k/a stop p
- KEmax = eVs - saturation photocurrent = when all electrons reach to anode
- then photocurrent is k/a
- saturation photocurrent
- I diretcly proportional to 1/d^2
d - distance bw cathode plate and phton source
stopping potential graph ?
ppg 9 notes
effect of intensity?
intensity
- directly proportionnal to no. of photons
- directly proportional to saturation current
- stopping potential remains same
graph - notes pg 10
effect of frequency ?
frequency
- directly proportional to stopping potential
- saturation current remains same
- new 2 > new 1
photoelectric equation ?
incident energy = work function + KEmax
pg 10
graphs, slope, which value is greater
1. KEmax and new
2. Vs and new
notes
1. slope - h
2. slope - h/e
1.vo2 > vo1
2. new >/= new naught
lemda </= lemda naught
wht is quantum efficiency?
3 formulae
formual 3 in notes
pg 12
wht is matter wave?
wavelength associated with matter k/a matter wave.
- cant detect mater wave of macro object
dual nature of light?
particle and wave
lemda formulae
1. photon
2. any particle
3. variations of 2.
4. graph bw lemda and momentum
5. graph bw lemda and 1/momentum
notes pg 15
lemda for electron
lemda ^2 for electron
lemda p for electron
pg 16 notes
if charge particle is moving in 90 degree transeverse magnetic field path ciruclar
r =
lemda =
r = mv/qb
lemda = h/mv
= h/rqb
mass and chrge of
proton
deutron
alpha
- m , q
- 2m , q
- 4m , 2q
debroglie wavelength
given by -
formula -
- bohr’s model
- nh/2pie = mvr
