The sun subtends an angle of `180^(@)` to our eyes form sunrise to sunset. But to the eyes of a fish this angle is `98^(@)` - explain.

A round balloon of radius 10m subtends an angle of 60^@ at the eye of the observer while the angle of elevation of its centre is 30^@ . Which of the following is the height of the centre of the balloon?

If the diameter of the sun subtends an angle of 32' at the eye of the observer and the diameter of the moon 30' and if the distance of the sun be 360 times that of the moon , find the ratio of the diameter of the sun of that of the moon.

The sun subtends an angle (1^(@))/(2) at the pole of a concave mirror. If the radius of curvature of the mirror is 15 m , what will be the size of the sun's image formed by the mirror?

The sum subtends an angle 0.5^(@) at the center of a concave mirror having radius of curvature 1 m. What will be the diameter of the image of the sun formed by the mirror?

Rays from the sun subtend an angle theta (in radian) at the pole of a concave mirror of focal length f. If the diameter of the sun is D the diameter of the image of the sun formed by the mirror is-

A small astronomical telescope has an objective of focal length 50 cm and an eyepiece of focal length 5 cm . It is focussed at the sun and the final image is formed at a distance of 25 cm from the eyepiece . If the diameter of the sun subtends an angle of 32' at the centre of the objective calculate the angular magnification of the instrument and the actual size of the image.

A spherical balloon of radius r subtends an angle alpha at the eye of anb observer. If the angle of elevation of the cerntre of the balloon be beta , then prove that the height of the balloon is r cosec (alpha)/(2) sin beta.