JEE Main 2018 Question Paper (16-Apr-2018) (Shift 1)

Question 1

The relative uncertainty in the period of a satellite orbiting around the Earth is $10^{-2}$. If the relative uncertainty in the radius of the orbit is negligible, the relative uncertainty in the mass of the Earth is:

Accepted Answer

$2 	imes 10^{-2}$

Answer

$6 	imes 10^{-2}$

Answer

$3 	imes 10^{-2}$

Answer

$10^{-2}$

Question 2

At some instant, a radioactive sample $ S_1 $ having an activity has twice the number of nuclei as another sample $ S_2 $ which has an activity of. The ratio of half-lives of $ S_1 $ and $ S_2 $ is

Accepted Answer

$4:1$

Answer

$1:4$

Answer

$1:2$

Answer

$2:1$

Question 3

Two moles of helium are mixed with $ n $ moles of hydrogen. If $\frac{C_p}{C_v} = \frac{3}{2}$ for the mixture, then the value of $ n $ is,

Accepted Answer

2

Answer

1

Answer

3

Answer

$\frac{3}{2}$

Question 4

Unpolarized light of intensity $ I $ is incident on a system of two polarizers, $ A $ followed by $ B $. The intensity of emergent light is $ \frac{I}{2} $. If a third polarizer $ C $ is placed between $ A $ and $ B $, the intensity of emergent light is reduced to $ \frac{I}{3} $. The angle between the polarizers $ A $ and $ C $ is $ \theta $, then

Accepted Answer

$ \cos 	heta = \left(\frac{2}{3}ight)^{\frac{1}{4}} $

Answer

$ \cos 	heta = \left(\frac{1}{3}ight)^{\frac{1}{4}} $

Answer

$ \cos 	heta = \left(\frac{1}{3}ight)^{\frac{1}{2}} $

Answer

$ \cos 	heta = \left(\frac{2}{3}ight)^{\frac{1}{2}} $

Question 5

The de-Broglie wavelength $\left(\lambda_{B}\right)$ associated with the electron orbiting in the second excited state of the hydrogen atom is related to that in the ground state $\left(\lambda_{G}\right)$ by:

Accepted Answer

$\lambda_{B} = 3 \lambda_{G}$

Answer

$ \lambda_{B} = 2 \lambda_{G} $

Answer

$ \lambda_{B} = \lambda_{\frac{G}{3}} \quad $

Answer

$ \lambda_{B} = \lambda_{\frac{G}{2}} $