46.If you use a microscope to watch smoke particles in still air, you will see them moving about all the time. This phenomenon is called

47.Given below are two statements, labelled as Assertion (A) and Reason (R). In the context of the two statements, which of the following is correct ?Assertion (A) : Plants when kept in oxygen free atmosphere survive longer in light than in dark.Reason (R) : In light, plants produce oxygen due to photosynthesis and manyfacture their own food.

48.The lightest particle of matter is

49.Cover of capsule is made of

50.Given below are two statements, labelled as Assertion (A) and Reason (R). In the context of the two statements, which of the following is correct ?Assetion (A) : The edges of shadows cause by objects when light falls on them are sharp.Reason (R) : Diffraction of of light at an edge produces a redistribution of intensity at the edge of the shadow.