A ray of light passing through an equilateral prism is having velocity $2.12 \times 10^8 \mathrm{~m} / \mathrm{s}$ in the prism material, then the minimum angle of deviation is

$\_\_\_\_$ degrees.

Light source having wavelength 331 nm is used to generate photo-electrons whose stopping potential is 0.2 V . The work function of the used metal in the experiment is $\alpha \times 10^{-19} \mathrm{~J}$. The value of $\alpha$ is $\_\_\_\_$ .

$$ \left(\mathrm{h}=6.62 \times 10^{-34} \mathrm{~J} \mathrm{~s}, \mathrm{e}=1.6 \times 10^{-19} \mathrm{C} \text { and } \mathrm{c}=3 \times 10^8 \mathrm{~m} / \mathrm{s}\right) $$

A compound microscope is designed with two symmetric biconvex lenses. The objective lens is cut vertically, creating two identical plano-convex lenses. One of them is used in place of original objective lens. To retain same magnification keeping the object distance unchanged, the tube length has to be

Two wires as shown in the figure below, made of steel and have breaking stress of $12 \times 10^8 \mathrm{~N} / \mathrm{m}^2$. Area of cross-section of upper wire is $0.008 \mathrm{~cm}^2$ and of lower wire is $0.004 \mathrm{~cm}^2$. The maximum mass that can be added to pan without breaking any wire is $\_\_\_\_$ kg.