A moving ship continuously sends in ultrasonic pulses down to the sed-bed and records the time delays of the reflected pulses. The variation of time delays recorded versus the positions of the ship is plotted in the following graph. Which of the position indicates the deepest sea bed?

1. A
2. B
3. C
4. D

Mechanical energy is equal to

1. the sum of total energy and potential energy
2. the sum of potential energy and kinetic energy
3. the energy acquired by machines
4. All of the above

Observe the heating curve of water

Which of the following represent boiling?

1. OA
2. AB
3. BC
4. CD

A ray of light travels from a medium of refractive index n₁ to a medium of refractive index n₂. If angle of incidence is i and angle of refraction is r, then $\dfrac{\text{sin i}}{\text{sin r}}$ is equal to

1. n₁

2. n₂

3. $\dfrac{\text{n}$2}{\text{n}1}

4. $\dfrac{\text{n}$1}{\text{n}2}