xiii) Without green house effect, the average temperature of Earth's surface would have been: a) -18°C b) 33°C c) 0°C d) 15°C xiv) How many plane mirrors are used in a periscope &... xiii) Without green house effect, the average temperature of Earth's surface would have been: a) -18°C b) 33°C c) 0°C d) 15°C xiv) How many plane mirrors are used in a periscope & a kaleidoscope a) 2 & 3 respectively b) 3 each c) 3 & 2 respectively d) 2 & 4 respectively xv) For a convex mirror, the value of u is always ______ & the value of v is ______ a) Positive, Positive b) Positive, Negative c) Negative, Negative d) Negative, Positive Question 2 i) The gravitational potential energy stored in a box of weight 150kgf is 1.5 × 10^4 J. Find the height of the box. Take 1kgf = 10N. ii) Explain the term 'Green House Effect'. Name the radiations which are absorbed by the greenhouse gases. iii) How does an optician increase the effective length of his room by using a mirror? Where does he place the sign board? iv) Can a body possess energy even when it is not in motion? Explain your answer with an example. v) State Pascal's law of transmission of pressure. vi) Explain why a gas bubble released at the bottom of a lake grows in size as it rises to surface of Lake. vii) The diagram below shows the three different movements of the diver. How does the liquid pressure on the diver change in each of the following cases? Read more

xiii) a) -18°C xiv) a) 2 & 3 respectively xv) d) Negative, Positive Question 2 Solutions provided above.

xiii) a) -18°C

xiv) a) 2 & 3 respectively

xv) d) Negative, Positive

Question 2 i) 10m

ii) The greenhouse effect is a natural process that warms the Earth's surface. When the Sun's energy reaches the Earth's atmosphere, some of it is reflected back to space and the rest is absorbed and re-radiated by greenhouse gases. The absorbed energy warms the atmosphere and the surface of the Earth. Greenhouse gases absorb infrared radiation.

iii) The optician places a mirror on the wall opposite the sign board. This creates a virtual image of the room, effectively doubling its length. He places the sign board in front of the mirror (but closer to the customer) so that its reflection appears further away, making the room seem larger.

iv) Yes, a body can possess potential energy even when it is not in motion. For example, a book on a shelf has gravitational potential energy due to its height above the ground.

v) Pascal's law states that pressure applied to a fluid in a closed container is transmitted equally to every point of the fluid and the walls of the container.

vi) As a gas bubble rises in a lake, the pressure around it decreases because the water pressure decreases with decreasing depth. According to Boyle’s Law (PV = constant), as the pressure decreases, the volume of the gas bubble increases, causing it to grow in size.

vii) a) Pressure increases as the diver goes deeper. b) Pressure remains the same as the diver moves horizontally at the same depth c) Pressure decreases as the diver ascends.