WBJEE 2026 Physics and Chemistry Question Paper (24-May-2026)

Question 1

A body of density '$\rho$' is dropped slowly on the surface of a lake of depth $d$. If the density of the lake water be '$\rho'$' ($\rho' < \rho$) then the time taken by the body to reach the bottom of the lake is

Accepted Answer

$\left[ \frac{2d\rho}{g(\rho - \rho')} \right]^{\frac{1}{2}}$

Answer

$\left[ \frac{2gd}{\rho(\rho - \rho')} \right]^{\frac{1}{2}}$

Answer

$\left[ \frac{2d\rho'}{\rho g(\rho - \rho')} \right]^{\frac{1}{2}}$

Answer

$\left[ \frac{g(\rho - \rho')}{2d\rho} \right]^{\frac{1}{2}}$

Question 2

Beyond what distance, the ray optics is sufficiently valid when the aperture is $6	ext{ mm}$ wide and the wavelength is $6000	ext{ \AA}$?

Accepted Answer

$60	ext{ m}$

Answer

$50	ext{ m}$

Answer

$40	ext{ m}$

Answer

$10	ext{ m}$

Question 3

A plano-convex lens fits exactly into a plano-concave lens. Their plane surfaces are parallel to each other. If lenses are made of different materials of refractive indices $\mu_1$ and $\mu_2$ and $R$ is the radius of curvature of the curved surface of the lenses, then the focal length of the combination is

Accepted Answer

$\frac{R}{(\mu_1 - \mu_2)}$

Answer

$\frac{2R}{(\mu_1 - \mu_2)}$

Answer

$\frac{R}{2(\mu_1 + \mu_2)}$

Answer

$\frac{R}{2(\mu_1 - \mu_2)}$

Question 4

Consider a fuse wire of length $l$ and radius $r$. The time of heating ($t$) for passing the maximum current will depend on

Accepted Answer

$t \propto r^4 l^0$

Answer

$t \propto r^2 l$

Answer

$t \propto r^3 l^2$

Answer

$t \propto r^2 l^3$

Question 5

Density and volume of a body are given as $(20 \pm 4)	ext{ gm/cm}^3$ and $(10 \pm 1)	ext{ cm}^3$ respectively. The absolute error in measurement of mass is

Accepted Answer

$60	ext{ gm}$

Answer

$20	ext{ gm}$

Answer

$30	ext{ gm}$

Answer

$45	ext{ gm}$