Answer:
14. Mirror is made up of a very smooth surface, whereas wall is not made up of a smooth surface. Smooth surfaces reflect the incident light to more extent, where as rough surfaces absorb most of the incident light. Hence, the reflected light from walls can't form the image and wall can't act as a mirror.
15. Correct answer is d) About four years
16. Correct answer is b) Convex lens
Explanation:
15. If the light from the nearest star (Alpha Centauri) takes more than 4 years to reach us, we're seeing that star 4 years in the past.
16. Refracting telescopes use convex lenses, at the front of a tube, to gather and focus incoming light. The image formed is magnified for the viewer through an eyepiece lens at the back end of the tube.
