Question

describe any activity to illustrate the phenomenon of phototropism and explain why does this occurs

Answer 1

Phototropism is the movement of part of the plant in response to light. The main factor responsible for it is differential movement of Auxin concentration towards the shaded area when unidirectional light is provided. So, the part which is in shade grows more and particular part of plant tilt towards source of light. see NCERT pg 121 of science for activity
 

Answer 2

"Phototropism:

Growth is the response to a light stimulus called phototropism. The cells of the plants react with auxin which is a chemical substance present in light therefore, shoots are grown up towards the light.

Activity:

• Fill with water a conical flask.
• Cover the flask's neck with a wire mesh.
• Keep on the wire mesh two or three freshly sprouted beam seeds.
• Take a one-sided open cardboard box.
• Keep the flash in the box so that the open side of the box faces light from the window.
• Then we observed shoots grown up towards the light and roots are away from the light."