How can bats ascertain distances, directions, nature and size of the obstacles without eyes ?

Explain why (or how): Bats can ascertain distances, directions, nature, and sizes of the obstacles without any “eyes”,

A compound lens is made of a convex lens of power 10 D and a concave lens of power 5 D. An object 2 cm high is placed in front of this combination at a distance 40 cm from it. Find nature and size of the image formed.

A compound lens is made of a convex lens of power 10 D and a concave lens of power 5 D. An object 2 cm high is placed in front of this combination at a distance 40 cm from it. Find nature and size of the image formed.

The human eye can focus object at different distances by adjusting the focal length of the eye lens this is due to:

A small candle, 2.5 cm in size is placed at 27 cm in front of a concave mirror of radius of curvature 36 cm. At what distance from the mirror should a screen be placed in order to obtain a sharp image? Describe the nature and size of the image. If the candle is moved closer to the mirror, how would the screen have to be moved?

How does a combination of lenses affect the size, position and nature of the image?

Can one have inductance without a resistance ? How about a resistance without an inductance?

Consider a sunlike start at a distance of 2 parsecsWhen it is seen through a telescope with 100 magnification, what should be the angular size of the star? Sun appears to be (1//2)^@ from the earth. Due to atmospheric fluctuationsw, eye can't resolve objects smaller than 1 arc minute.