Download App

Dual Nature of Radiation and Matter — Physics STD 12 Science — Question

Rajasthan BoardEnglish MediumSTD 12 SciencePhysicsDual Nature of Radiation and Matter3 Marks
Question
The work function for the following metals is given: $Na: 2.75 eV; K: 2.30 eV; Mo: 4.17 eV; Ni: 5.15 eV.$ Which of these metals will not give photoelectric emission for a radiation of wavelength $3300 \mathring A$ from a $He-Cd$ laser placed $1 m$ away from the photocell? What happens if the laser is brought nearer and placed $50 \ cm$ away?
✓

Answer

$Mo$ and $Ni$ will not show photoelectric emission in both cases
Wavelength for a radiation, $\lambda=3300\ \mathring{\text{A}}=3300\times10^{-10}\ \text{m}$
Speed of light, $c = 3 \times 10^8 m/s$
Planck's constant, $h = 6.6 \times 10^{-34} Js$
The energy of incident radiation is given as:
$\text{E}=\frac{\text{hc}}{\lambda}$
$=\frac{6.6\times10^{-34}\times3\times10^{8}}{3300\times10^{-10}}=6\times10^{-19}\ \text{J}$
$\frac{6\times10^{-19}}{1.6\times10^{-19}}=3.158\ \text{eV}$
It can be observed that the energy of the incident radiation is greater than the work function of $Na$ and $K$ only.
It is less for $Mo$ and $Ni.$
Hence, $Mo$ and $Ni$ will not show photoelectric emission.
If the source of light is brought near the photocells and placed $50 \ cm$ away from them,
then the intensity of radiation will increase. This does not affect the energy of the radfation.
Hence, the result will be the same as before.
However, the photoelectrons emitted from $Na$ and $K$ will increase in proportion to intensity.

Need a full question paper?

Generate a complete, print-ready paper with questions like this in minutes — across 16+ boards, with answer keys.

Start Generating Free

Explore more

More "3 Marks Question" from Dual Nature of Radiation and Matter→Dual Nature of Radiation and Matter — all question types→Physics STD 12 Science question papers→Rajasthan Board STD 12 Science question papers→Rajasthan Board question paper generator→

Similar questions

In Fizeau method of measuring the speed of light, the toothed wheel is placed in the focal plane of a converging lens. How would the experiment be affected if the wheel is slightly away from the focal plane?
→
Calculate the magnetic dipole moment corresponding to the motion of the electron in the ground state of a hydrogen atom.
→
A semiconducting material has a band gap of 1eV. Acceptor impurities are doped into it which create acceptor levels 1meV above the valence band. Assume that the transition from one energy level to the other is almost forbidden if kT is less than $\frac{1}{50}$ of the energy gap. Also, if kT is more than twice the gap, the upper levels have maximum population. The temperature of the semiconductor is increased from 0K. The concentration of the holes increases with temperature and after a certain temperature it becomes approximately constant. As the temperature is further increased, the hole concentration again starts increasing at a certain temperature. Find the order of the temperature range in which the hole concentration remains approximately constant.
→
$A$ charge of $+2.0 \times 10^{-8}C$ is placed on the positive plate and a charge of $-1.0 \times 10^{-8}C$ on the negative plate of a parallel $-$ plate capacitor of capacitance $1.2\times10^{-3}\mu\text{F}.$ Calculate the potential difference developed between the plates.
→
A charge of 1.0C is placed at the top of your college building and another equal charge at the top of your house. Take the separation between the two charges to be 2.0km. Find the force exerted by the charges on each other. How many times of your weight is this force?
→
Find the charges on the three capacitors connected to a battery as shown in figure. Take $\text{C}_1=2.0\mu\text{F},\ \text{C}_2=4.0\mu\text{F},\ \text{C}_3=6.0\mu\text{F}$ and V = 12 volts.
→
The product of the hole concentration and the conduction electron concentration turns out to be independent of the amount of any impurity doped. The concentration of conduction electrons in germanium is $6 \times 10^{19}$ per cubic metre. When some phosphorus impurity is doped into a germanium sample, the concentration of conduction electrons increases to $2 \times 10^{23}$ per cubic metre. Find the concentration of the holes in the doped germanium.
→
A transverse wave of amplitude 0.50mm and frequency 100Hz is produced on a wire stretched to a tension of 100N. If the wave speed is 100m/s, what average power is the source transmitting to the wire?
→
Let x and a stand for distance. Is $\int\frac{\text{dx}}{\sqrt{\text{a}^2-\text{x}^2}}=\frac{1}{\text{a}}\sin^{-1}\frac{\text{a}}{\text{x}}$ dimensionally correct?
→
If the operating potential in an X-ray tube is increased by 1%, by what percentage does the cutoff wavelength decrease?
→