EASY
JEE Main
IMPORTANT
Earn 100

Monochromatic light (that is, light of a single wavelength) is to be absorbed by a sheet of photographic film and thus, recorded on the film. Photon absorption will occur if the photon energy equals or exceeds 0.6 eV, the smallest amount of energy needed to dissociate an AgBr molecule in the film. (a) What is the greatest wavelength of light that can be recorded by the film? (b) In what region of the electromagnetic spectrum is this wavelength located?

Important Questions on Photons and Matter Waves

EASY
JEE Main
IMPORTANT
Under ideal conditions, a visual sensation can occur in the human visual system if the light of wavelength 550 nm is absorbed by the eye's retina at a rate as low as 110 photons per second. What is the corresponding rate at which energy is absorbed by the retina?
HARD
JEE Main
IMPORTANT
Light of wavelength 200 nm shines on an aluminum surface, 4.20 eV is required to eject an electron. What is the kinetic energy of (a) the fastest and (b) the slowest ejected electrons? (c) What is the stopping potential for this situation? (d) What is the cutoff wavelength for aluminum?
HARD
JEE Main
IMPORTANT
For the thermal radiation from an ideal blackbody radiator with a surface temperature of 2000 K, let Ic represent the intensity per unit wavelength according to the classical expression for the spectral radiation and IP represents the corresponding intensity per unit wavelength according to the Planck's expression. What is the ratio Ic/IP for a wavelength of (a) 400 nm (at the blue end of the visible spectrum) and (b) 200 μm (in the far infrared)?
(c) Does the classical expression agree with the Planck's expression in the shorter wavelength range or the longer wavelength range? 
HARD
JEE Main
IMPORTANT
The meter was once defined as 1650763.73 wavelengths of the orange light emitted by a source containing Krypton-86 atoms. What is the photon energy of that light?
HARD
JEE Main
IMPORTANT

In equation ψ(x,t)=Aei(kx-ωt)+Be-i(kx+ωt) keep both terms, putting A=B=ψ0. The equation then describes the superposition of two matter waves of equal amplitude, travelling in opposite directions. (Recall that this is the condition for a standing wave.) (a) Show that |Ψ(x,t)|2 is then given by,

|Ψ(x,t)|2=2ψ02[1+cos 2 kx].

(b) Plot this function and demonstrate that it describes the square of the amplitude of a standing matter-wave. (c) Show that the nodes of this standing wave are located at x=(2n+1)14λ, where n=0,1,2,3, ... and λ is the de Broglie wavelength of the particle. (d) Write a similar expression for the most probable locations of the particle.

HARD
JEE Main
IMPORTANT
X rays with a wavelength of 71 pm are directed onto a gold foil and eject tightly bound electrons from the gold atoms. The ejected electrons then move in circular paths of radius r in a region of uniform magnetic field B. For the fastest of the ejected electrons, the product Br is equal to 1.88×10-4 T m. Find (a) the maximum kinetic energy of those electrons and (b) the work done in removing them from gold atoms.
HARD
JEE Main
IMPORTANT
What are (a) the energy of a photon corresponding to wavelength 1.00 nm, (b) the kinetic energy of an electron with de Broglie wavelength 1.00 nm, (c) the energy of a photon corresponding to wavelength 1.00 fm and (d) the kinetic energy of an electron with de Broglie wavelength 1.00 fm?