Atoms — Physics STD 12 Science — Question

A glass slab of thickness 3 cm and refractive index 3/2 is placed on ink mark on a piece of paper. For a person looking at the mark at a distance 5.0 cm above it, the distance of the mark will appear to be

(a) 3.0 cm

(b) 4.0 cm

(c) 4.5 cm

(d) 5.0 cm

'Electrons revolve round the nucleus in well-defined orbits, like planets revolve round the sun' was the brainchild of:

An inductor, a resistance and a capacitor are joined in series with an AC source. As the frequency of the source is slightly increased from a very low value, the reactance:

1. Of the inductor increases.
2. Of the resistor increases.
3. Of the capacitor increases.
4. Of the circuit increases.

Assertion  :  The temperature coefficient of resistance is positive for metals and negative for P-type semiconductor. 

Reason     : The effective charge carriers in metals are negatively charged whereas in P-type semiconductor they are positively charged.

(a) If both assertion and reason are true and the reason is the correct explanation of the assertion.

(b) If both assertion and reason are true but reason is not the correct explanation of the assertion.

(c) If assertion is true but reason is false.

(d) If the assertion and reason both are false.

The maximum magnification that can be obtained with a convex lens of focal length 2.5 cm is (the least distance of distinct vision is 25 cm)

(a) 10

(b) 0.1

(c) 62.5

(d) 11

A current carrying long solenoid is placed on the ground with its axis vertical. A proton is falling along the axis of the solenoid with a velocity v. When the proton enters into the solenoid, it will

(a) Be deflected from its path

(b) Be accelerated along the same path

(c) Be decelerated along the same path

(d) Move along the same path with no change in velocity

A light source approaches the observer with velocity 0.8 c. The doppler shift for the light of wavelength  5500 Å is

(a) 4400 Å

(b) 1833 Å

(c) 3167 Å

(d) 7333 Å

Assertion  :  The earth’s magnetic field does not affect the working of a moving coil galvanometer.

Reason     : Earth’s magnetic field is very weak.

(a) If both assertion and reason are true and the reason is the correct explanation of the assertion.

(b) If both assertion and reason are true but reason is not the correct explanation of the assertion.

(c) If assertion is true but reason is false.

(d) If the assertion and reason both are false.

Find the value of x in the following nuclear reaction.
₇​N¹⁴ + ₂​He⁴ → _x​O¹⁷ + _1​H¹

Inductance plays the role of