1900's Physics and Wave

Q.

How do You find the Speed of an Electron?

Q. Calculate wavelength, frequency wave number of light whose period is $2\times {10}^{-10}$ second.

Q.

What is a radio wave?

Q.

Carbon dioxide is ____ times heavier than air.

Q. In ground state, the radius of hydrogen atom is $0.53\mathring{A}$. The radius of $L{i}^{2+}$ ion Z = 3 in the same state is

1. 
2. 
3. 
4. 

Q. Colours in thin films are because of:

1. Polarisation
2. Interference
3. Reflection
4. Diffraction

Q.

How the average speed is different from speed?

Q. The ionic radii of A+ and B- ions are 1.62A and 2.8A, what is the no of second nearest neighbour of anion?

Q. The work function of a metal is 4.2 eV. If the radiation of 2000 Å falls on the metal, then kinetic energy of the fastest photoelectron is

1. 1.66 × 10^-19 J

2. 3.22 × 10^-19 J

3. 1.66 × 10^-20 J

4. 3.22 × 10^-18 J

Q.

The nucleus of an atom can be assumed to be spherical. The radius of the nucleus of mass number A is given by $1.25\times {10}^{-13}\times A^{\frac{1}{3}}$ Radius of atom is one A . If the mass number is 64, then the fraction of the atomic volume that is occupied by the nucleus is

1. 1.0 X 10^-3

2. 2.5 X 10^-2

3. 5.0 X 10^-5

4. 1.25 X 10^-13

Q. On a rainy day, small oil films on water show brilliant colours. This is due to:

1. Dispersion
2. Interference
3. Diffraction
4. Polarisation

Q. Which has the maximum atomic radius-

1. $Al$
2. $Si$
3. $P$
4. $Mg$

Q.

What is a homogenous reaction?

Q.

Energy of an electron increases with increase in distance from the nucleus. Comment on the change in kinetic energy and potential energy.

Q.

Two identical photocathodes receive the light of frequencies $f_1$ and $f_2$ respectively. If the velocities of the photo-electrons coming out are $v_1$ and $v_2$ respectively, then:

1. $v_1+v_2={\left[\frac{2h}{m}\left(f_1+f_2\right)\right]}^{\frac{1}{2}}$

2. $v_1-v_2={\left[\frac{2h}{m}\left(f_1-f_2\right)\right]}^{\frac{1}{2}}$

3. ${v_1}^2+{v_2}^2=\frac{2h}{m}\left(f_1+f_2\right)$

4. ${v_1}^2-{v_2}^2=\frac{2h}{m}\left(f_1-f_2\right)$

Q.

If a semiconductor photodiode can detect a photon with a maximum wavelength of$400nm$, then its band gap energy is? Planck’s constant $h=6.63\times {10}^{-34}J.s$. Speed of light $c=3\times {10}^{8}m/s$.

1. $1.5eV$

2. $2.0eV$

3. $3.1eV$

4. $1.1eV$

Q.

Energy of photoelectrons is independent of the _ of incident radiation.

A. Wavelength

B. Wavenumber

C. Frequency

D intensity

Q.

Among 4p, 4s, 3p and 3d orbitals, the 3d orbital has the least energy.

1. True
2. False

Q.

State the basic postulates of Bohrs theory of atomic spectra.

Q.

Out of the following which one is not a possible energy for a photon to be emitted by hydrogen atom according to Bohrs atomic model ?

1. $0.65eV$

2. $1.9eV$

3. $11.1eV$

4. $13.6eV$

Q. Specific conductance of 0.1M HA is $3.75\times {10}^{-4}oh{m}^{-1}c{m}^{-1}$. If ${\lambda }^{\infty }$ of HA is $250oh{m}^{-1}c{m}^{2}mo{l}^{-1}$, then dissociation constant Ka of HA is

1. $1\times {10}^{-5}$
2. $2.25\times {10}^{-4}$
3. $2.25\times {10}^{-5}$
4. $2.25\times {10}^{-13}$

Q.

Two balls of equal mass undergo head-on collision while each was moving with a speed of $6m/s$. If the coefficient of restitution is $1/3$, the speed of each ball after impact will be

Q.

The activity of a radioactive sample is measured as N₀ counts per minute at t = 0 and N₀/e counts per minute at t = 5 minutes. The time (in minutes) at which the activity reduces to half its value is

1. $5\mathrm{lo}{g}_{e}2$

2. ${\log }_{e}2/5$

3. $5/{\log }_{e}2$

4. $5{\log }_{10}2$

Q. PE is -27.2 eV in second or bit of He+ ion then calculate, double of total energy in first excited state of H atom

Q. Interference of light is an evidence that:

1. Light is a transverse wave
2. The speed of light is very large
3. Light has wave phenomenon
4. Light is an electromagnetic wave

Q. A hydrogen atom in the ground state is excited by monochromatic radiation of wavelength $\lambda \dot{A}$. The resulting spectrum consists of maximum 15 different lines. What is the wavelength $\lambda$?

1. $450.63\dot{A}$
2. $635.38\dot{A}$
3. $937.3\dot{A}$
4. None of these

Q.

Which of the following is the energy of a possible excited state of hydrogen?

Q.

What is the ratio of shortest wavelength of the Balmer series to the shortest wavelength of Lyman series?

1. $4:1$

2. $4:3$

3. $4:9$

4. $5:9$

Q.

An electron, practically at rest, is initially accelerated through a potential difference of $100\mathrm{V}$ . It then has a de Broglie wavelength $={\lambda }_1\mathrm{\AA }$. It then gets retarded through $19\mathrm{V}$ and then has wavelength ${\lambda }_2\mathrm{\AA }$. A further retardation through $32\mathrm{V}$ changes the wavelength to ${\lambda }_3\mathrm{\AA }$. What is $\frac{{\lambda }_3-{\lambda }_2}{{\lambda }_1}$

1. $\frac{10}{63}$

2. $\frac{20}{63}$

3. $\frac{40}{63}$

4. $\frac{1}{63}$

Q.

The wavelength of the radiation emitted, when a hydrogen atom electron falls from infinity to stationary state 1, would be (Rydberg constant =1.097×10⁷ m^-1)

1. 406 nm

2. 192 nm

3. 91 nm

4. $9.1\times {10}^{-8}$ nm