A lizard, at an initial distance of 21 cm behind an insect moves from rest with an acceleration of $2 \mathrm{~cm} / \mathrm{s}^2$ and pursues the insect which is crawling uniformly along a straight line at a speed of $20 \mathrm{~cm} / \mathrm{s}$. Then the lizard will catch the insect after :

In a full wave rectifier circuit operating from $$50$$ $$Hz$$ mains frequency, the fundamental frequency in the ripple would be

A nuclear transformation is denoted by $$X\left( {n,\alpha } \right)\matrix{ 7 \cr 3 \cr } Li.$$ Which of the following is the nucleus of element $$X$$ ?

The diagram shows the energy levels for an electron in a certain atom. Which transition shown represents the emission of a photon with the most energy?