Question 1 :
Electrons are accelerated through a potential difference of V = 10 kV. The minimum wavelength λ_min of the X-ray emitted is-

Question 2 :
Sodium and copper have work functions {tex} 2.3 \mathrm { eV } {/tex} and {tex} 4.5 \mathrm { eV } {/tex} respectively. Then the ratio of the wavelengths is nearest to

Question 3 :
The largest distance between the interatomic planes of a crystal is 10^-7 cm. The upper limit for the wavelength of X-rays which can be usefully studied with this crystal is-

Question 4 :
Wave theory cannot explain the phenomena of ;<br>(A) Polarization (B) Diffraction<br>(C) Compton effect (D) Photoelectoric effect<br>Which of the following is correct?

Question 5 :
Which phenomenon best supports the theory that matter has a wave nature?

Question 7 :
An electron jumps from n = 4 to n = 1 state in H-atom. The recoil momentum of H-atom (in eV/C) is

Question 8 :
The ratio of the wavelengths for 2 &rarr; 1 transition in Li⁺⁺, He⁺ and H is

Question 9 :
What is the force exerted by a photon of intensity 1.4 kWm^-2 if it falls on a perfect absorber of radius 2 metre ?

Question 10 :
Which of the following devices is sometimes called an electric eye?

Question 11 :
1 g of hydrogen is converted into 0.993 g of helium in a thermonuclear reaction. The energy released is

Question 12 :
Light of wavelength &lambda; strikes a photo-sensitive surface and electrons are ejected with kinetic energy E. If the kinetic energy is to be increased to 2E, the wavelength must be changed to &lambda;' where -

Question 13 :
The count rate of a Geiger-Muller counter for the radiation of radioactive material of half life of 30 minutes decreases to 5 s^-1 after 2 hours. The initial count rate was -

Question 14 :
The masses of two radioactive substances are same and their half-lives are 1 year and 2 years respectively. The ratio of their activities after six years will be-

Question 15 :
In Thomson mass spectrograph when only electric field of strength 20 kV/m is applied, then the displacement of the beam on the screen is 2 cm. If length of plates = 5 cm, distance from centre of plate to the screen = 20 cm and velocity of ions = 10⁶m/s, then q/m of the ions is

Question 16 :
If the half-lives of a radioactive element for &alpha; and &beta; decay are 4 year and 12 years respectively, then the percentage of the element that remains after 12 year will be -

Question 17 :
In Thomson experiment of finding e/m for electrons, beam of electron is replaced by that of muons (particle with same charge as of electrons but mass 208 times that of electrons). No deflection condition in this case satisfied if

Question 18 :
Wave property of electrons implies that they will show diffraction effects. Davisson and Germer demonstrated this by diffracting electrons from crystals. The law governing the diffraction from a crystal is obtained by requiring that electron waves reflected from the planes of atoms in a crystal interfere constructively (see figure)<br><img style='object-fit:contain' src="https://data-screenshots.sgp1.digitaloceanspaces.com/5da967b06bacaa43595cb984.jpg" /><br>If a strong diffraction peak is observed when electrons are incident at an angle {tex} i {/tex} from the normal to the crystal planes with distance {tex} d {/tex} between them (see figure), de Broglie wavelength {tex} \lambda _ { d B } {/tex} of electrons can be calculated by the relationship {tex} ( n {/tex} is an integer)

Question 19 :
&mu;-meson is a particle which has charge same as that of the electron and mass 207 times the mass of electron. A &mu;-mesonic atom is formed when a &mu;-meason is captured by proton. The ionization energy of such an atom is-

Question 20 :
If a source of power {tex} 4 \mathrm { kW } {/tex} produces {tex} 10 ^ { 20 } {/tex} photons/second, the radiation belongs to a part of the spectrum called

Question 21 :
<font>Light rays of wavelengths 6000 Å and of photon intensity 39.6 watt/m</font>^{<font>2</font>}<font> is incident on a metal surface. If only one percent of photons incident on surface emit photoelectrons, then the number of electrons emitted per second per unit area from the surface will be : (h = 6.64 × 10</font>^{<font>-34</font>}<font> J-s, velocity of light = 3 × 10</font>^{<font>8</font>}<font> m/s)</font></p>

Question 22 :
<font>In the fission of U-235, the percentage of mass converted into energy is about-</font></p>

Question 23 :
<font>A Daniel cell is balanced on 125 cm lengths of a potentiometer wire. Now the cell is short circuited by a resistance 2</font><font face="Symbol, serif"><font></font></font><font> and the balance is obtained at 100 cm. The internal resistance of the Daniel cell is</font></p>

Question 24 :
<font>The number of neutrons in a chain reaction increases in -</font></p>

Question 25 :
<font>The half life period of a radioactive element X is same as the mean life time of another radioactive element Y. Initially both of them have the same number of atoms. Then -</font></p>