Modern phy - 1 Flashcards
(32 cards)
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
