Physics 2nd Paper CQ-Rajshahi Board-2019

1. In the above picture, an electron returns to the third orbit from the fourth orbit of an atom in a photo experiment. As a result, a photon emerges. It is worth mentioning that, value of Planck's constant, mass of electron, charge of electron and permeability at vacuum is $\quad 6.63 \times 10^{-34} \mathrm{JS}, \quad 9.1 \times 10^{-31} \mathrm{~kg}$, $1.6 \times 10^{-19} \mathrm{C}$ and $8.854 \times 10^{-12} \mathrm{C}^{2} \mathrm{~N}^{-}$ $\mathrm{m}^{-2}$ respectively.

2.

Where, $O P=O A=O B=10 \mathrm{~cm}, O P \perp A B$. The charge $q_{1}$ is at point $A$ and charge $q_{2}$ in $B$.

3. In this figure PQRS represents a rectangular electric circuit core which is placed perpendicularly in a magnetic field of magnitude $B$ and the plane of the circuit PQRS is in parallel to the magnetic field.

[Given that, $\mathrm{B}=1.5 \times 10^{-2} \mathrm{wb} \cdot \mathrm{m}^{-2}, \mathrm{I}=2 \mathrm{~A}, \mathrm{I}=1 \mathrm{~m}$, and $\mathrm{B}=0.5 \mathrm{~m}$ ]

4. Fahim is a student of physics. He performed an experiment of photoelectric emission by using two light rays of wavelengths $4 \times 10^{-7} \mathrm{~m}$ and $7.8 \times 10^{-7} \mathrm{~m}$ respectively. In his experiment work function of the used metal is $2.3 \mathrm{eV}$.

[Given that, $1 \mathrm{eV}=1.6 \times 10^{-19} \mathrm{~J}, \mathrm{~h}=6.63 \times 10^{-34} \mathrm{~J} . \mathrm{S}, \mathrm{C}=$ $3 \times 10^{8} \mathrm{~m} / \mathrm{s}$ ]

5.

Here, $\mathrm{I}_{\mathrm{c}}=35 \mathrm{~mA}$.