Nucleus — Physics STD 12 Science — Question

A charge of 10 e.s.u. is placed at a distance of 2 cm from a charge of 40 e.s.u. and 4 cm from another charge of 20 e.s.u. The potential energy of the charge 10 e.s.u. is (in ergs)(a) 87.5(b) 112.5(c) 150(d) 250

The net electric flux through a closed surface is:

Assertion :   The threshold frequency of photoelectric effect supports the particle nature of sunlight.
Reason      : If frequency of incident light is less than the threshold frequency, electrons are not emitted from metal surface.(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 electromagnetic wave of highest frequency is :

Consider a light beam incident from air to a glass slab at Brewster's angle as shown in Fig. A polaroid is placed in the path of the emergent ray at point P and rotated about an axis passing through the centre and perpendicular to the plane of the polaroid.

Which one of the following is known as Saptarishi (a) Orion (b) Ursa major(c) Ursa minor(d) Scorpion

Identify the correct statement from the following.

When a beam of accelerated electrons hits a target, a continuous X-ray spectrum is emitted from the target. Which of the following wavelength is absent in the X-ray spectrum, if the X-ray tube is operating at 40,000 volts(a) 0.25 Å(b) 0.5 Å(c) 1.5 Å  (d) 1.0 Å

Two long straight wires are kept parallel, distance between them is 2R and current is flowing in opposite directions in two wires. The magnitude of magnetic field at a point midway between them which is at a distance R from each wire is: