Questions

Thermal energy is caused by the motion of atoms and molecules in the matter.

1. Thermal energy is an example of kinetic energy, as it is due to the motion of particles, with motion being the key.
2. Thermal energy results in an object or a system having a temperature that can be measured.
3. Thermal energy can be transferred from one object or system to another in the form of heat.

Concave type of glasses are used in the headlights of the vehicles as the light from the bulb which is at focus will converges out and spreads and reflects back parallely.

At least one black can be chosen in two ways from each box:
Now, probability of choosing at least one black ball from first box 

= 1/2 × [ (2C1× 2C1)/4C2 + 2C2/ 4C2 ]= 5/12

Probability of choosing at least one black ball from 2nd box
= 1/2 × [(4C1×12C1)/16C2 + 4C2/ 16C2] = 9/40

Final probability

= 5/12 + 9/40 = (50 + 27)/120 = 77/120