NTA JEE Main 7th April 2013 Online

The amplitude of a damped oscillator decreases to 0.9 times its original magnitude in 5s. In another 10s it will decrease to $$\alpha$$ times its original magnitude, where $$\alpha$$ equals :

The magnetic field in a travelling electromagnetic wave has a peak value of 20 nT. The peak value of electric field strength is :

The graph between angle of deviation ($$\delta$$) and angle of incidence ($$i$$) for a triangular prism is represented by :

Diameter of a plano-convex lens is 6 cm and thickness at the centre is 3 mm. If the speed of light in the material of lens is $$2 \times 10^8$$ m s$$^{-1}$$, the focal length of the lens is:

A beam of unpolarised light of intensity $$I_0$$ is passed through a polaroid A and then through another polaroid B which is oriented so that its principle plane makes an angle of 45° relative to that of A. The intensity of the emergent light is:

Two coherent point sources $$S_1$$ and $$S_2$$ are separated by a small distance $$d$$ as shown in the figure. The fringes obtained on the screen will be

The anode voltage of a photocell is kept fixed. The wavelength $$\lambda$$ of the light falling on the cathode is gradually changed. The plate current I of the photocell varies as follows :

In a hydrogen like atom electron makes transition from an energy level with quantum number n to another with quantum number (n - 1). If n >> 1, the frequency of radiation emitted is proportional to :

A diode detector is used to detect an amplitude modulated wave of 60% modulation by using a condenser of capacity 250 pico farad in parallel with a load resistance of 100 kilo ohm. Find the maximum modulated frequency which could be detected by it.

The I-V characteristics of an LED is: