Embibe Experts Solutions for Chapter: Modern Physics, Exercise 1: BITSAT 2017

A radioactive sample of half life $23.1 \mathrm{days}$ is disintegrating continuously. The percentage decay of the sample between the ${15}^{\mathrm{th}}$ and ${16}^{\mathrm{th}}$ day will be [Take, $e^{0.03}=1.03$]

$12 \mathrm{eV}$ energy is given to electron in third orbit of $\mathrm{H}$-atom, then final energy of electron when it ionise from third orbit, is

Some amount of a radioactive substance (half-life $=10$ days ) is spread inside a room and consequently, the level of radiation becomes $50$ times the permissible level for normal occupancy of the room. After how many days will the room be safe for occupation?

The frequency and the intensity of incident beam of light falling on the surface of a photoelectric material is increased by a factor of two. This will

When photon of energy $4.0 \mathrm{eV}$ strikes the surface of a metal $A$, the elected photoelectrons have maximum kinetic energy $T_A \mathrm{eV}$ and de-Broglie wavelength ${\lambda }_A$. The maximum kinetic energy of photoelectron liberated from another metal $B$ by photon of energy $4.50 \mathrm{eV}$ is $T_B=\left(T_A-1.50\right) \mathrm{eV}$. If the de-Broglie wavelength of these photoelectrons ${\lambda }_B=2{\lambda }_A$, then choose the correct statement(s).

The activity of a radioactive sample is measured as $N_0$ counts per minute at $t=0$ and $\frac{N_0}{e}$ counts per minute at $t=5 \min$. The time (in minutes) at which the activity reduces to half its value is

Monochromatic radiation of wavelength $\lambda$ is incident on a hydrogen sample in ground state. Hydrogen atom absorbs a fraction of light and subsequently emits radiations of six different wavelengths. The wavelength $\lambda$ is

An $\alpha$-particle after passing through potential difference of $V$ volt collides with a nucleus. If the atomic number of the nucleus is $Z$, then distance of closest approach is