1. Suppose your near point is 25.0 cm and you want to obtain a magnifying power
ID: 1520625 • Letter: 1
Question
1. Suppose your near point is 25.0 cm and you want to obtain a magnifying power of 20 with a simple magnifier. What focal-length lens should you choose?(II was incorrect when I did it)
Question options:
80 cm
25 cm
20 cm
1.3 cm
1.0 m
2. If the near point of your eye is 80.0 cm, what power of reading glasses should you use to bring your near point to 25.0 cm? (III was incorrect when I did it)
Question options:
22.0
27.5
12.5
-1.25
-5.25
3.A diverging lens has a focal length of magnitude 20 cm. An object is placed 10 cm in front of the diverging lens. Calculate the magnification of the image and whether it is upright or inverted. (II was incorrect when I did it)
Question options:
0.67 upright
0.52 upright
0.85 inverted
0.67 inverted
1.5 upright
4.The optical path for visible light in a lens is(III was incorrect when I did it)
Question options:
the same as the geometrical path.
independent of the material of which the lens is constructed.
the same as the optical path for ultraviolet.
the same no matter what portion of the lens it passes through.
is increased when the index of refraction is increased.
Please answer all parts, there are 4 of them and show what is the final answer in each part!!
I)80 cm
II)25 cm
III)20 cm
IV)1.3 cm
V)1.0 m
Explanation / Answer
As mangification is given as
M = q / P
20 = q / P
20P = q
by the formula
1 / f = 1 / p + 1/q
f = pq / p+ q
putting the values
f =( q / 20) q / ( q / 20 + q)
f = o.20 /( q + 0.20q ) / 0.20
f = o.202 / 1.20q
f = o.202 / 1.20(.25)
= 13.3cm
So, option( iii) is the closer answer and would be the right option
2) same calculation is involve as in part 1 , iii would be the correct answer.
3) 1 / f = 1 / p + 1 / q
p= qf /( q+f)
p = 20cm (10cm) / 30cm
p = 6.6cm
Mangification = M = q / P = 10/ 6.6 =1.51 ( upright)
( V ) is the correct option
V) increase d when the index of refration is increased.
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