In Astronomical Observations, Signals Observed from the Distant Stars Are Generally Weak. If the Photon Detector Receives a Total of 3.15 × 10–18 J from the Radiations of 600 Nm, - Chemistry


In astronomical observations, signals observed from the distant stars are generally weak. If the photon detector receives a total of 3.15 × 10–18 J from the radiations of 600 nm, calculate the number of photons received by the detector.



From the expression of energy of one photon (E),

`"E" = "hc"/lambda`

λ = wavelength of radiation

h = Planck’s constant

c = velocity of radiation

Substituting the values in the given expression of E:

`"E" = ((6.626 xx 10^(-34) " Js")(3xx10^(8) ms^(-1)))/((600xx10^(-9) " m"))`

Energy of one photon = 3.313 × 10–19 J

Number of photons received with 3.15 × 10–18 J energy

`= (3.15 xx 10^(-18) " J")/(3.313 xx 10^(-19)" J")`

= 9.5


  Is there an error in this question or solution?
Chapter 2: Structure of Atom - EXERCISES [Page 72]


NCERT Chemistry Part 1 and 2 Class 11
Chapter 2 Structure of Atom
EXERCISES | Q 2.48 | Page 72


Yellow light emitted from a sodium lamp has a wavelength (λ) of 580 nm. Calculate the frequency (ν) and wave number (`bar v`) of the yellow light.

A 25-watt bulb emits monochromatic yellow light of the wavelength of 0.57μm. Calculate the rate of emission of quanta per second.

Electrons are emitted with zero velocity from a metal surface when it is exposed to radiation of wavelength 6800 Å. Calculate threshold frequency (v0) and work function (W0) of the metal.

Following results are observed when sodium metal is irradiated with different wavelengths. Calculate (a) threshold wavelength and, (b) Planck’s constant.

λ (nm) 500 450 400
v × 10-5 (cm s-1) 2.55 4.35 5.35

The electron energy in the hydrogen atom is given by En = (–2.18 × 10–18)/n2 J. Calculate the energy required to remove an electron completely from the n = 2 orbit. What is the longest wavelength of light in cm that can be used to cause this transition?

The work function for caesium atom is 1.9 eV. Calculate

  1. the threshold wavelength and
  2. the threshold frequency of the radiation. If the caesium element is irradiated with a wavelength 500 nm, calculate the kinetic energy and the velocity of the ejected photoelectron.

If travelling at same speeds, which of the following matter waves have the shortest wavelength?

Which of the following will not show deflection from the path on passing through an electric field?

A hypothetical electromagnetic wave is shown in Figure. Find out the wavelength of the radiation.

What is photoelectric effect? State the result of photoelectric effect experiment that could not be explained on the basis of laws of classical physics. Explain this effect on the basis of quantum theory of electromagnetic radiations.


      Forgot password?
Use app×