JEE 2013 :: Advanced 2013 :: Physics 2013

• Advanced 2013 - Physics 2013
• Advanced 2013 - Chemistry 2013
• Advanced 2013 - Mathematics 2013

Two non-reactive monoatomic ideal gases have their atomic masses in the ratio 2:3. The ratio of their partial pressures, when enclosed in a vessel kept at a constant temperature, is 4:3.
The ratio of their densities is 

Answer:

Explanation:

$\rho=\frac{P M}{RT}$
   $\therefore$   $\rho\propto p M$

or   $\frac{\rho_{1}}{\rho_{2}}=\left(\frac{p_{1}}{p_{2}}\right)\left(\frac{M_{1}}{M_{2}}\right)$

$=\left(\frac{2}{3}\right)\left(\frac{4}{3}\right)=\frac{8}{9}$

In the Young's double-slit experiment using a monochromatic ;light of wavelength λ the path difference (in terms of an integer n)  corresponding  to any point having half the peak intensity is 

Answer:

Explanation:

$I= I_{max} \cos^{2}\frac{\phi}{2}$    ...............(i)

  Given,         $I= \frac{I_{max}}{2}$.........(ii)

 From Eqs( i) and (ii) , we have

   $\phi= \frac{\pi}{2}, \frac{3\pi}{2}, \frac{5\pi}{2}$  

  Or path difference ,  $\triangle x=\left(\frac{\lambda}{2\pi}\right).\phi$

  $\therefore$     $\triangle x=\frac{\lambda}{4},\frac{3\lambda}{4},\frac{5\lambda}{4},.....(\frac{2n+1}{4})\lambda$

The pulse of light duration 100 ns is absorbed completely by a small object initially at rest. Power of pulse is 30mV and the speed of light is 3 x10⁸  ms^-1. The final momentum of object is 

Answer:

Explanation:

final momentum of object =  Power x time / speed of light

               = $\frac{30\times 10^{-3}\times 100\times10^{-9}}{3\times 10^{8}}=1.0\times 10^{-17}kg-m/s$

Two  rectangular blocks , having indentical dimensions, can be arranged either in configuration 1 or in configuration  II as shown in the figure. One of the blocks  has thermal conductivity  K and  the other 2K. The  temperature difference between the ends along the x-axis is the same in both configuratiuons. It takes 9s to  transport  a certain  amount of heat from the hot end to the cold  end in the configuration I,  The time to transport the same amount of heat in the configuration II is

Answer:

Explanation:

$R_{1}=R_{1}+R_{2}=\left(\frac{l}{KA}\right)+\left(\frac{l}{2KA}\right)=\frac{3}{2}\left(\frac{l}{KA}\right)$

$\frac{1}{R_{II}}=\frac{1}{R_{1}}+\frac{1}{R_{2}}=\frac{KA}{l}+\frac{2KA}{l}$

or   $  R_{II}=\frac{l}{3KA}=\frac{R_{1}}{4.5}$

since thermal resistance R_II is 4.5 times less than thermal resistance R₁

$\therefore$    $ t_{II}=\frac{t_{I}}{4.5}=2 s$

A ray of light travelling in the direction   $\frac{1}{2}(\hat{i}+\sqrt{3}\hat{j})$  is inciodent on a plane mirror. after reflection, it travels along the  direction   $\frac{1}{2}(\hat{i}-\sqrt{3}\hat{j})$  . The angle of incidence is 

Answer:

Explanation:

Component along the plane=1/2  and component perpendicular to the plane = $\frac{\sqrt{3}}{2}$

 $\therefore$     $\tan i=\frac{(\frac{1}{2})}{(\frac{\sqrt{3}}{2})}=\frac{1}{\sqrt{3}}$

 $\therefore$     i= $30^{0}$   = angle of incidence

• Advanced 2013 - Physics 2013
• Advanced 2013 - Chemistry 2013
• Advanced 2013 - Mathematics 2013