31.

In R-L-C seres circut, the potential differences across each element is 20 V. Now the value of the resistance alone is doubled, then P.D. across R, L and C respectively

• 20 V, 10 V, 10 V

• 20 V, 20 V, 20 V

• 20 V, 40 V, 40 V

• 10 V, 20 V, 20 V

A rectangular coil of 100 turns and size 0.1 m x 0.05 m is placed perpendicular to a magnetic field of 0.1 T. If the field drops to 0.05 T in 0.05 s, the magnitude of the e.m.f. imuuced in the coil is

• $\sqrt{2}$ V

• $\sqrt{3}$ V

• 0.5 V

• $\sqrt{6}$ V

In the circuit diagram, heat produces in R, 2R and 1.5 R are in the ratio of

• 4 : 2 : 3

• 8 : 4 : 27

• 2 : 4 : 3

• 27 : 8 : 4

A series combination of resistor (R), capacitor (C) is connected to an A.C. source of angular frequency. Keeping the voltage same, if the frequency is changed to ω/3, the current becomes half of the original current. Then the ratio of the capacitive reactance and resistance at the former frequency is

• $\sqrt{0.6}$

• $\sqrt{3}$

• $\sqrt{2}$

• $\sqrt{6}$

Pick out the correct statement from the following

• Mercury vapour lamp produces line emission spectrum

• Oil flame produces line emission spectrum

• Band spectrum helps us to study molecular structure

• Sunlight spectrum is an example for line absorption spectrum

The figure shows the energy level of certain atom. When the electron de excites from 3E to E, an electromagentic wave of wavelength λ, is emitted. What is the wavelength of the electromagnetic wave emitted when the electron de excites from $\frac{5\mathrm{E}}{3} \mathrm{to} \mathrm{E}$ ?

• 3λ

• 2λ

• 5λ

• $\frac{3\mathrm{\lambda }}{5}$

The speed of light in media M₁ and M₂ are 1.5 x 10⁸ ms^-1 and 2 x 10⁸ ms^-1 respectively. A ray travels from medrum M₁ to the medium M₂ with an angle of incidence θ. The ray suffers total internal reflection. Then the value of the angle of incidence θ is

• $> {\sin }^{-1} \left(\frac{3}{4}\right)$

• $< {\sin }^{-1} \left(\frac{3}{4}\right)$

• $= {\sin }^{-1} \left(\frac{3}{4}\right)$

• $\le {\sin }^{-1} \left(\frac{3}{4}\right)$

Which of the following phenomena suppor tthe wave theory of light ? 

1. Scattering
2. Interference
3. Diffraction
4. Velocity of light in a denser medium is less than the velocity of light in the rare medium.

• 1, 2 and 3

• 1, 2 and 4

• 2, 3 and 4

• 1, 3 and 4

White light reflected from a soap film (Refractive Index = 1.5) has a maxima at 600 nm and a minima at 450 nm with no minimum in between. Then the thickness of the film is

• 1

• 2

• 3

• 4

A cylindrical tube of length 0.2 m and radius R with sugar solution of concentration C produce a rotation of θ in the plane of vibration of a plane polanzed light. The same sugar solution is transferred to another tube of length 0.3 m of same radius. The remaining gap is filled by distilled water. Now the optical rotation produced is

• θ

• $2 \frac{\mathrm{\theta }}{3}$

• $3 \frac{\mathrm{\theta }}{2}$

• $9 \frac{\mathrm{\theta }}{4}$