The focal length of the field lens (which is an achromatic combination of two lenses) of telescope is 90 cm. The dispersive powers of the two lenses in the combination are 0.024 and 0.036. The focal lengths of two lenses are ____.
30 cm and 60 cm
30 cm and – 45 cm
45 cm and 90 cm
15 cm and 45 cm
The focal lengths of the objective and the eye piece of a compound microscope are 2.0 cm and 3.0 cm, respectively. The distance between the objective and the eye piece is 15.0 cm. The final image formed by the eye piece is at infinity. The two lenses are thin. The distance in cm of the object and the image produced by the objective, measured from the objective lens, are respectively
2.4 and 12.0
2.4 and 15.0
2.0 and 12.0
2.0 and 3.0
In a compound microscope, the intermediate image is
Virtual, erect and magnified
Real, erect and magnified
Real, inverted and magnified
Virtual, erect and reduced
An astronomical telescope has an angular magnification of magnitude 5 for distant objects. The separation between the objective and the eyepiece is 36 cm and the final image is formed at infinity. The focal length fo of the objective and the focal length fo of the eyepiece are
fo= 45 cm and fe =-9cm
fo= 50 cm and fe =10cm
fo= 7.2 cm and fe =5cm
fo= 30 cm and fe =6cm
1 and 2
3 and 4
A reflecting telescope has a large mirror for its objective with radius of curvature equal to 64 cm. If the eyepiece has a focal length of 3.2 cm, calculate the magnifying power of the telescope.
15
25
30
10
A convex lens of length 10 cm is used as a magnifying glass. The image is formed at a distance of 25 cm from the lens, then, the magnifying power is
4.5
3.5
2.5
1.5
The sum the focal length of the objective and an eye-piece, in case on an astronomical telescope is equal to ____.
the length of the telescope
half the length of the telescope
double the length of the telescope
None of the above