Question

Q.8. What is fossils ?
Or
Define homologous organ.
Q.9. Define the centre of curvature of the spherical mirror ?
Or
Define the principle focus of a concave mirror.​

Answer 1

Explanation:

Q8. Answer: Fossils are any impressions or imprints left by some previous organism in soft mud or sedimentary rocks, which subsequently hardened. Fossils are also moulds and casts of entire organisms that got preserved. Fossils are documentary evidences of organic evolution.

Homologous organs are defined as the organs of different animals that are having a similar structure but differ in their functions. The structure of the two different animals resemble but the functions of their organs vary.

Centre of curvature of a spherical mirror is defined as the centre of the sphere of which the spherical mirror is a part. ... The point where reflected ray converges or appears to be diverging from is known as focus of the mirror and its distance from the pole is known as focal length (f).

The principle focus of concave mirror is a point on its principle axis to which all the light rays which are parallel and close to the axis, converge after reflection from the mirror