EXERCISE 19

Potential difference applied to an X -ray tube is $5\mathrm{kV}$ and the current through it is $3.2 \mathrm{mA}$. The number of electrons striking the target per second is Take $e=1.6\times {10}^{-19}\mathrm{C}$

Hard X-rays for the study of fractures in bones should have a minimum wavelength of ${10}^{-11} \mathrm{m}$. The accelerating voltage for electrons in X -rays machine should be 

The anode voltage of a photocell is kept fixed. The wavelength $\lambda$ of the light falling on the cathode is gradually changed. The plate current I of the photocell varies as follows. Fig. $19.18$

When monochromatic point source of light is at a distance of $0.2 \mathrm{m}$ from a photoelectric cell, the cut-off voltage and the saturation current are respectively $0.6$ volt and $18.0 \mathrm{mA}$. If the same source is placed $0.6 \mathrm{m}$ away from the photoelectric cell, then

A $200 \mathrm{W}$ sodium street lamp emits yellow light of wavelength $0.6\mathrm{\mu m}$. Assuming it to be $25\%$ efficient in converting electrical energy to light, the number of photons of yellow light it emits per second is:

Two radiations of photons energy $1\mathrm{eV}$ and $2.5\mathrm{eV}$, successively illuminate a photosensitive metallic surface of work function $0.5\mathrm{eV}$. The ratio of the maximum speeds of the emitted electrons is

Which of the following facts about the photoelectric effect can be understood without involving the quantum concept of light propagation ?

In the case of photoelectric effect,