If the image formed by a lens for all positions of an object placed in front of it is always erect and diminished, what is the nature of this lens? Draw a ray diagram to justify your answer. If the numerical value of the power of this lens is 10 D, what is its focal length in the Cartesian system?

How did Mendel explain that it is possible that a trait is inherited but not expressed in an organism?

‘‘Evolution and classification of organisms are interlinked.’’ Give reasons to justify this statement.

State the cause of dispersion of white light by a glass prism. How did Newton, using two identical glass prisms, show that white light is made of seven colours? Draw a ray diagram to show the path of a narrow beam of white light, through a combination of two identical prisms arranged together in an inverted position with respect to each other, when it is allowed to fall obliquely on one of the faces of the first prism of the combination.

Water is an elixir of life, a very important natural resource. Your Science teacher wants you to prepare a plan for a formative assessment activity, ‘‘How to save water, the vital natural resource’’. Write any two ways that you will suggest to bring awareness in your neighbourhood, on ‘how to save water’.