A ray of light is incident on a glass slab at angle i. The emergent ray is: MCQ with Answer and Explanation

Explanation:
A CRO uses an electron beam sweeping across a phosphorescent screen to create a visible graph. It is fundamentally a voltage-measuring instrument. The vertical deflection is directly proportional to the applied voltage, and the horizontal deflection is controlled by a time-base generator, allowing it to display voltage waveforms over time.

Explanation:
Magnetic field lines form concentric circles around a straight current-carrying wire, with direction given by right-hand thumb rule (thumb in current direction, fingers curl in field direction). This is derived from Biot-Savart law or Ampère's circuital law. Memory tip: 'Right-hand rule: thumb = current, fingers = field circles'. This fundamental field pattern is frequently tested in competitive exams. Always visualize field direction: for current toward you, field lines are counterclockwise. Distinguish from solenoid field (axial inside) or bar magnet (dipole pattern).

Explanation:
Control rods (made of cadmium, boron, or hafnium) absorb neutrons to regulate the fission chain reaction rate. Inserting rods deeper reduces neutron population, slowing reaction; withdrawing them increases reaction rate. Moderators (water, graphite) slow neutrons to thermal energies for efficient fission. Memory aid: 'Control rods = neutron absorbers; Moderators = neutron slowers'. This application question tests knowledge of reactor components, common in competitive exams. Always distinguish roles: fuel (fissionable material), moderator, control rods, coolant.