Read the passage given below and attempt the following questions on the passage:
Astronomical Telescope :
An instrument used to view distant objects clearly. It consists of—
(a) Objective lens
(b) Eyepiece
Working of Telescope :
The telescope is used to provide angular magnification of distant objects. The objective has a large focal length and a much larger aperture than the eyepiece because object is very far away. Light from a distant object enters the objective and a real and inverted image is formed at its second focal point. This image acts as an object for the eyepiece; it magnifies this image producing a final inverted image.
(a) Objective lens
(b) Eyepiece
Working of Telescope :
The telescope is used to provide angular magnification of distant objects. The objective has a large focal length and a much larger aperture than the eyepiece because object is very far away. Light from a distant object enters the objective and a real and inverted image is formed at its second focal point. This image acts as an object for the eyepiece; it magnifies this image producing a final inverted image.
Magnification :
The magnifying power m is the ratio of the angle β subtended at the eye by the final image to the angle α which the object subtends at the lens or the eye. Therefore, m≈ (β /α) ≈ (h/fe)x(fo/h)=(fo/fe). In this case, the length of the telescope tube is (fo+fe).
The magnifying power m is the ratio of the angle β subtended at the eye by the final image to the angle α which the object subtends at the lens or the eye. Therefore, m≈ (β /α) ≈ (h/fe)x(fo/h)=(fo/fe). In this case, the length of the telescope tube is (fo+fe).
A) The magnifying power of a telescope is 9. In normal adjustment the distance between objective and eyepiece is 20 cm. What is the the focal length of objective and eyepiece lenses in cm?
a)15,5
b) 18,2
c) 20,1
d) 10,10
B) In normal adjustment position of object and final image is at
a) object at infinity and image at least distance of distinct vision.
b) object is at infinity and image is at infinity
c) both at least distance of distinct vision.
d) object at least distance of distinct vision and image at infinity.
C) If four lenses are given with Power of lens given below
P : +5D Q: +1D R:+20 D S:+10D
For getting value of maximum magnification which combination is most suitable for lenses to be taken as objective and as eyepiece:
a) Q and R
b) Q and S
c) P and Q
d) R and S
D) In option C the maximum magnification of telescope is:
a) 20
b) 10
c) 5
d) 50
E) In option C with maximum magnification the length of astronomical telescope formed will be:
a) 100 cm
b) 95cm
c) 90 cm
d) 105 cm.
a)15,5
b) 18,2
c) 20,1
d) 10,10
B) In normal adjustment position of object and final image is at
a) object at infinity and image at least distance of distinct vision.
b) object is at infinity and image is at infinity
c) both at least distance of distinct vision.
d) object at least distance of distinct vision and image at infinity.
C) If four lenses are given with Power of lens given below
P : +5D Q: +1D R:+20 D S:+10D
For getting value of maximum magnification which combination is most suitable for lenses to be taken as objective and as eyepiece:
a) Q and R
b) Q and S
c) P and Q
d) R and S
D) In option C the maximum magnification of telescope is:
a) 20
b) 10
c) 5
d) 50
E) In option C with maximum magnification the length of astronomical telescope formed will be:
a) 100 cm
b) 95cm
c) 90 cm
d) 105 cm.
A) b) B) b) C) a) D) a) E) d)
