Current Electricity — Physics STD 12 Science — Question

When a ray of light passes from a denser to a rarer medium:

Rate of change of torque τ with deflection θ is maximum for a magnet suspended freely in a uniform magnetic field of induction B, when(a) θ = 0°(b) θ = 45°(c) θ = 60°(d) θ = 90°

The concept of solid angle is a natural extension of a angle to dimensions.

A concave and convex lens have the same focal length of 20 cm and are put into contact to form a lens combination. The combination is used to view an object of 5 cm length kept at 20 cm from the lens combination. As compared to the object, the image will be(a) Magnified and inverted(b) Reduced and erect (c) Of the same size as the object and erect(d) Of the same size as the object but inverted

Which of the following element was discovered by study of Fraunhofer lines(a) Hydrogen(b) Oxygen(c) Helium(d) Ozone

Capacitance (C) of the capacitor is.

In an NPN transistor the collector current is 24 mA. If 80% of electrons reach collector its base current in mA is(a) 36(b) 26(c) 16       (d) 6

Assertion :  No interference pattern is detected when two coherent sources are infinitely close to each other.
Reason     : The fringe width is inversely proportional to the distance between the two slits.(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.

X-rays are in nature similar to(a) Beta rays(b) Gamma rays(c) de-Broglie waves(d) Cathode rays