# 1900's Physics and Wave

## Trending Questions

**Q.**

How do You find the Speed of an Electron?

**Q.**Calculate wavelength, frequency wave number of light whose period is 2×10−10 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 ˚A. The radius of Li2+ ion Z = 3 in the same state is

**Q.**Colours in thin films are because of:

- Polarisation
- Interference
- Reflection
- 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

1.66 × 10

^{-19}J3.22 × 10

^{-19}J1.66 × 10

^{-20}J3.22 × 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 1.25×10−13×A13 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

1.0 X 10

^{-3}2.5 X 10

^{-2}5.0 X 10

^{-5}1.25 X 10

^{-13}

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

- Dispersion
- Interference
- Diffraction
- Polarisation

**Q.**Which has the maximum atomic radius-

- Al
- Si
- P
- 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:

${v}_{1}+{v}_{2}={\left[\frac{2h}{m}\left({f}_{1}+{f}_{2}\right)\right]}^{\frac{1}{2}}$

${v}_{1}-{v}_{2}={\left[\frac{2h}{m}\left({f}_{1}-{f}_{2}\right)\right]}^{\frac{1}{2}}$

${{v}_{1}}^{2}+{{v}_{2}}^{2}=\frac{2h}{m}\left({f}_{1}+{f}_{2}\right)$

${{v}_{1}}^{2}-{{v}_{2}}^{2}=\frac{2h}{m}\left({f}_{1}-{f}_{2}\right)$

**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 $c=3\times {10}^{8}m/s$.

$1.5eV$

$2.0eV$

$3.1eV$

$1.1eV$

**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.

- True
- 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 ?

$0.65eV$

$1.9eV$

$11.1eV$

$13.6eV$

**Q.**Specific conductance of 0.1M HA is 3.75×10−4ohm−1cm−1. If λ∞ of HA is 250ohm−1cm2mol−1, then dissociation constant Ka of HA is

- 1×10−5
- 2.25×10−4
- 2.25×10−5
- 2.25×10−13

**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 N_{0} counts per minute at t = 0 and N_{0}/e counts per minute at t = 5 minutes. The time (in minutes) at which the activity reduces to half its value is

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

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

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

$5{\mathrm{log}}_{10}2$

**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:

- Light is a transverse wave
- The speed of light is very large
- Light has wave phenomenon
- Light is an electromagnetic wave

**Q.**A hydrogen atom in the ground state is excited by monochromatic radiation of wavelength λ ˙A. The resulting spectrum consists of maximum 15 different lines. What is the wavelength λ?

- 450.63 ˙A
- 635.38 ˙A
- 937.3 ˙A
- 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?

$4:1$

$4:3$

$4:9$

$5:9$

**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 $\frac{{\lambda}_{3}-{\lambda}_{2}}{{\lambda}_{1}}$

$\frac{10}{63}$

$\frac{20}{63}$

$\frac{40}{63}$

$\frac{1}{63}$

**Q.**

The wavelength of the radiation emitted, when a hydrogen atom electron falls from infinity to stationary state 1, would be (Rydberg constant =1.097×10^{7} m^{-1})

406 nm

192 nm

91 nm

9.1×10−8 nm