Which compound are responsible for the depletion of ozone layer?

Which out of the two spherical mirrors, has positive focal length? Which out of the two, will form a real and inverted image, at its ‘F’ point which can be taken on the screen.

(a) one –half of a convex lens is covered with a black paper. Will such a lens produce an image of the complete object? Support your answer with a ray diagram.

(b) An object 5 cm high is held 25 cm away from a converging lens of focal length 10 cm.

(i) Draw the ray diagram and

(ii) Calculate the position and size of the image formed.

(iii) What is the nature of the image?

Define, ‘trophic level’.

Write the electron dot structure of ethene molecule, C₂H₄.