Some constellations, such as ursa minor, are visible in the sky year-round; other constellations appear for only part of the year. explain why this happens.

As the Earth revolves about the sun, different sky is visible during time of the year. We have winter constellations and summer constellations. But some constellations appear through out the year like Ursa Minor are the ones which lie close to the poles. The Earth rotates about the axis passing through North and south pole. The axis always points towards North. Thus, the constellations near the Poles would be visible throughout the year.

d

explanation:

v=uf/(u-f)

= 5.10/(5-10) convex lens has positive focal length

=50/-5

=-10 cm (formed at other side)