A coin is placed at the bottom of a tin can. Move your eyes until the coin is just out of sight (see diagram). Keep your eyes in this position while someone pours water gradually into the tin can. What would you observe ? Explain your observation.

If you put one ice cube in a glass of water and another in a glass of alcohol, what would you observe ? Explain your observations.

Have you ever observed any water pollution in your area? What measures would you suggest to control it?

Explain how you can take care of your eyes

An object O is placed in front of a plane mirror MN as shown in the diagram. A student moves her eye along the line XY to observe the image of O. identify the point(s) on the line XY where the image of O can be seen.

A cylindrical vessel, whose diameter and height both are equal to 30 cm, is placed on a horizontal surface and a small particle P is placed in it at a distance of 5.0 cm from the centre. An eye is placed at a position such that the edge of the bottom is just visible (see figure 18-E8). The particle P is in the plane of drawing. Up to what minimum height should water be poured in the vessel to make the particle P visible ?