Continuous Spectrum

Q. The photoelectric threshold wavelength of silver is $3250\times {10}^{-10}m$. The velocity of the electron ejected from a silver surface by ultraviolet light of wavelength $2536\times {10}^{-10}m$ is

1. $0.6\times {10}^{6}m/s$
2. $61\times {10}^{3}m/s$
3. $0.3\times {10}^{6}m/s$
4. $8\times {10}^{8}m/s$

Q. The X-ray beam coming from an X-ray tube -

1. is monochromatic.
2. has all wavelengths smaller than a certain maximum wavelength.
3. has all wavelengths greater than a certain maximum wavelength.
4. has all wavelengths lying between a minimum and a maximum wavelength.

Q. The velocity by of the most energetic electrons emitted from a metallic surface is doubled when the frequency $\nu$ of the incident radiation is doubled. The work function of the metal is-

1. $\frac{2}{3}h\nu$
2. $\frac{h\nu }{2}$
3. $\frac{h\nu }{3}$
4. $\frac{h\nu }{4}$

Q. When a metal surface is illuminated by light of wavelengths $400\text{nm}$ and $250\text{nm},$ the maximum velocities of the photoelectrons ejected are $v$ and $2v$ respectively. The work function of the metal is$-[h=$Planck's constant, $c=$speed of light in vacuum$]$

1. $2hc\times {10}^6\text{J}$
2. $1.5hc\times {10}^6\text{J}$
3. $hc\times {10}^6\text{J}$
4. $0.5hc\times {10}^6\text{J}$

Q. The maximum kinetic energy of photoelectrons emitted from a metal surface when light of wavelength $\lambda$ is incident on it is $1\text{eV}$. When a light of wavelength $\frac{\lambda }{3}$ is incident on the surface, Maximum kinetic energy becomes $4\text{eV}$. The work function of the metal is

1. $\frac{hc}{\lambda }$
   
2. $\frac{hc}{3\lambda }$
   
3. $\frac{2hc}{\lambda }$
   
4. $\frac{hc}{2\lambda }$
   

Q. A metal surface is illuminated by light of two different wavelengths $250\text{nm}$ and $300\text{nm}.$ The maximum speeds of ejected electrons corresponding to these wavelengths are $v_1$ and $v_2$ respectively. If the ratio of $v_1:v_2=2:1.$The work function of the metal is nearly-
$[\text{Use}hc=1240\text{eV nm}]$

1. $3.7\text{eV}$
2. $2.8\text{eV}$
3. $3.85\text{eV}$
4. $2.5\text{eV}$

Q. The wavelength of the carrier waves in a modern optical fibre communication network is close to

1. $600nm$
2. $900nm$
3. $2400nm$
4. $1500nm$

Q. When the energy of the incident radiation is increased by $20\%$ the kinetic energy of the photoelectrons emitted from a metal surface increased from $0.5\text{eV}$ to $0.8\text{eV}$. The work functions of the metal is-

1. $0.65\text{eV}$
2. $1.0\text{eV}$
3. $1.3\text{eV}$
4. $1.5\text{eV}$

Q. Assertion : If an electron and proton possessing same kinetic energy enter an electric field in a perpendicular direction, the path of the electron is more curved than that of the proton. Reason : Electron forms a larger curve due to its small mass

Q. In YDSE, the distance between two slits are 0.03mm and distance between slits and the screen is 1.5m. If the fourth bright fringe is formed at a distance 1cm from the central bright fringe, then find the wavelength of the light used .

Q.

A potential difference of 20 kV is plied across and X - ray tube. The minimum wavelength of X-rays generated is ___Å. (IIT JEE 1996)

Q.

What physical quantity is the same for X-rays of wavelength 10⁻¹⁰ m, red light of wavelength 6800 Å and radiowaves of wavelength 500 m?

Q.

One of the following wavelengths is absent and the rest are present in the X-rays coming from a Coolidge tube. Which one is the absent wavelength?

1. 25 pm

2. 50 pm

3. 75 pm

4. 100 pm

Q. The frequency and intensity of a light source are doubled. Consider the following statements.
(A) The saturation photocurrent remains almost the same.
(B) The maximum kinetic energy of the photoelectrons is doubled.
(a) A and B are true.
(b) A is true but B is false.
(c) A is false but B is true.
(d) A and B are false.

Q.

An X-ray tube is operated at 66 kV. Then, in the continuous spectrum of the emitted X-rays

1. wavelengths 0.01 nm and 0.02 nm will both be present
2. wavelengths 0.01 nm and 0.02 nm will both be absent
3. wavelength 0.02 nm will be absent but wavelength 0.01 nm will be present
4. wavelength 0.01 nm will be absent but wavelength 0.02 nm will be present

Q. A potential difference of $15000\text{V}$ is applied across the ends of a copper target. The speed of the emitted X-Rays inside the tube is -

Assume standard values.

1. $3\times {10}^8\text{m/s}$
2. $3\times {10}^7\text{m/s}$
3. $3\times {10}^6\text{m/s}$
4. $3\times {10}^5\text{m/s}$

Q. In the continuous part of the spectrum of X-rays, the limiting frequency is

1. inversely proportional to the potential through which electrons have been accelerated
2. directly proportional to the accelerating potential
3. not dependent upon the acclerating potential
4. is dependent upon the nature of the target material

Q. For sky wave propagation, the radio waves must have a frequency range in between :

1. 45 MHz to 50 MHz
2. 35 MHz to 40 MHz
3. 1 MHz to 2 MHz
4. 5 MHz to 25 MHz

Q. (a) maximum frequency

Q. The photoelectric threshold wavelength of tungsten is $230nm$. The energy of electrons ejected from its surface by ultraviolet light of wavelength $180nm$ is

1. $0.15eV$
2. $1.5eV$
3. $15eV$
4. $15keV$

Q. The maximum kinetic energy of photoelectrons emitted from a metal surface when light of wavelength $\lambda$ is incident on it is $1\text{eV}$. When a light of wavelength $\frac{\lambda }{3}$ is incident on the surface, Maximum kinetic energy becomes $4\text{eV}$. The work function of the metal is

1. $\frac{hc}{\lambda }$
   
2. $\frac{hc}{3\lambda }$
   
3. $\frac{2hc}{\lambda }$
   
4. $\frac{hc}{2\lambda }$
   

Q. The resolving power of an electron microscope operated at 16 kV is R. The resolving power of the electron microscope when operated at 4 kV is

1. R/2
2. R/4
3. 4R
4. 2R

Q. A spectroscopic instrument can resolve two nearby wavelengths λ and λ + Δλ if λ/Δλ is smaller than 8000. This is used to study the spectral lines of the Balmer series of hydrogen. Approximately how many lines will be resolved by the instrument?

Q. The potential difference applied to an X-ray tube is increased. As a result, in the emitted radiation:

1. Bottom of the mirror should be at a height $85cm$
2. the intensity decreases
3. the minimum wavelength increases
4. the intensity increases
5. the minimum wavelength decreases

Q. Light of wavelength $\lambda =400nm$ falls on an isolated neutral metal ball of radius 1 m and work function 2.1 $eV$. Maximum number of photoelectrons that can be achieved from ball is $n\times {10}^7$, then here n is (take hc = 1240 eV nm) .(Write upto two digits after the decimal point)

Q. Figure shows the intensity-wavelength relations of X-rays coming from two different Coolidge tubes. The solid curve represents the relation for the tube A in which the potential difference between the target and the filament is $V_A$ and the atomic number of the target material is $Z_A$. These quantities are $V_B$ and $Z_B$ for the other tube. Then

1. $V_A>V_B,Z_A>Z_B$
2. $V_A>V_B,Z_A<Z_B$
3. $V_A<V_B,Z_A<Z_B$
4. $V_A<V_B,Z_A>Z_B$

Q. The phenomenon of diffraction can be exhibited by,

1. Infrared waves
2. Microwaves
3. X-rays
4. All of the above

Q. An X-ray tube operates on $30kV$. What is the minimum wavelength emitted
$(h=6.\times {10}^{-34}Js,e=1.6\times {10}^{-19}Columb,c=3\times {10}^{8}ms)$

1. $0.133A^o$
2. $0.4A^o$
3. $1.2A^o$
4. $6.6A^o$

Q. When a beam of accelerated electrons hits a target, a continuous x-ray spectrum is emitted from the target. Which of the following wavelength is absent in the x-ray spectrum if the x-ray tube is operating at 40, 000 volt?

1. 1.5 $A^0$
2. 0.5 $A^0$
3. 0.25 $A^0$
4. 1.0 $A^0$

Q. In an electron microscope the accelerating voltage is increased from 20 kV to 80 kV, the resolving power of the microscope will change from R to

1. $\frac{R}{2}$
2. $4R$
3. $3R$
4. $2R$