Mention the essential material (chemicals) to prepare soap in the laboratory. Describe in brief the test of determining the nature (acidic/alkaline) of the reaction mixture of saponification reaction.

A student very cautiously traces the path of a ray through a glass slab for different values of the angle of incidence (i). He then measures the corresponding values of the angle of refraction (r) and the angle of emergence (e) for every value of the angle of incidence. On analysing these measurements of angles, his conclusion would be

Study the following ray diagram:

In this diagram, the angle of incidence, the angle of emergence and the angle of deviation respectively have been represented by

Draw in sequence (showing the four stages), the process of binary fission in Amoeba.

A student focuses the image of a candle flame, placed at about 2 m from a convex lens of focal length 10 cm, on a screen. After that, he moves gradually the flame towards the lens and each time focuses its image on the screen.

A. In which direction does he move the lens to focus the flame on the screen?

B. What happens to the size of the image of the flame formed on the screen?

C. What difference is seen in the intensity (brightness) of the image of the flame on the screen?

D. What is seen on the screen when the flame is very close (at about 5 cm) to the lens?