VITEEE 2016 :: Physics :: General questions

• Physics - General questions

When a plastic thin film of refractiive index 1.45 is placed in the path of one of the interfering waves then the  central fringe is displaced through width of five fringes . The thickness of the film , if the wavelength of light is 5890 Å , will be 

Answer:

Explanation:

 $X_{0}=\frac{\beta}{\lambda}(\mu-1)t\Rightarrow5\beta=\frac{\beta (0.45)t}{5890\times 10^{-10}}$

$\therefore$    $t= \frac{5\times 5890\times 10^{-10}}{0.45}=6.544\times 10^{-4}cm$

Two lens of focal length f₁= 10 cm and f₂= -20 cm are kept as shown. The resultant power of combination will be

Answer:

Explanation:

$P= 2\left[\frac{100}{10}+\frac{100}{-20}+0\right]$

 P= 10 dipotre

A metal ball of mass 2 kg moving with a velocity of 36 km/h has a head on collision with a stationary ball of mass 3 kg. If  after the collision , the two balls move together , the loss in kinetic energy due to collision is 

Answer:

Explanation:

 Apply conservation of momentum

 m₁v₁ = (m₁+m₂)v

 $v= \frac{m_{1}v_{1}}{(m_{1}+m_{2})}$

 Here, v₁ = 36 km/hr=10 m/s

 m₁ =2 kg , m₂=3 kg

 $v= \frac{10\times2}{5}=4 m/s$

 K.E ( initial ) $= \frac{1}{2}\times2\times(10)^{2}=100 J$

K.E (final) $= \frac{1}{2}\times(3+2)\times(4)^{2}=40 J$

 Loss in K.E =100-40=60

Althernatively use this formula

$-\triangle E_{k}=\frac{1}{2}\frac{m_{1}m_{2}}{(m_{1}+m_{2})}(u_{1}-u_{2})^{2}$

A fish looking up through the water sees the outside world contained in a circular horizon. If  the refractive index of water is 4/3 and the fish is 12 cm below the surface, the radius of these circles (in cm) is 

Answer:

Explanation:

$\sin i_{c}=\frac{1}{\mu}=\frac{r}{\sqrt{r^{2}+h^{2}}}$

 using h=12 cm, $\mu$  =4/3

  we get  r= $\frac{36}{\sqrt{7}}$

 The magnetic flux in a closed circuit of resistance 10 Ω varies with time as  $\phi=(2t-4t^{2}+1)$ . the  current in the loop will change its direction after a time of

Answer:

Explanation:

$e=-\frac{d\phi}{dt}=[-2+8t+0]$

 $\Rightarrow 8t=2\Rightarrow t=\frac{1}{4}sec=0.25 sec$

• Physics - General questions