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All questions of Thin Lenses for EmSAT Achieve Exam
If R1 and R2 are the radii of curvature of a double convex lens, which of the following will have the largest power?- a)R1 = 10 cm and R2 = ∞
- b)R1 = R2 = 5 cm
- c)R1 = ∞ and R2 = 10 cm
- d)R1 = R2 = 10 cm
Correct answer is option 'B'. Can you explain this answer?
If R1 and R2 are the radii of curvature of a double convex lens, which of the following will have the largest power?
a)
R1 = 10 cm and R2 = ∞
b)
R1 = R2 = 5 cm
c)
R1 = ∞ and R2 = 10 cm
d)
R1 = R2 = 10 cm
|
Nikita Singh answered |
Using the lens maker’s formula we get
p= (μ−1) (1/R1+1/R2)
As we can clearly see, when R1= R2= 5cm then the maximum power is achieved.
p= (μ−1) (1/R1+1/R2)
As we can clearly see, when R1= R2= 5cm then the maximum power is achieved.
A convex lens produces a real image m times the size of the object. What is the distance of the object from the lens?- a)(m + 1)f
- b)
- c)(m – 1)f
- d)
Correct answer is option 'D'. Can you explain this answer?
A convex lens produces a real image m times the size of the object. What is the distance of the object from the lens?
a)
(m + 1)f
b)
c)
(m – 1)f
d)
|
Rajesh Gupta answered |
M=−ϑ /u =−m/1
ϑ=−mu
(1/ϑ)−(1/u)=1/f
1/mu+1/u=−1/f
(1+m)/xu=−1/f
u= (1+m)f/(m)
ϑ=−mu
(1/ϑ)−(1/u)=1/f
1/mu+1/u=−1/f
(1+m)/xu=−1/f
u= (1+m)f/(m)
A convergent lens made of crown glass (refractive index 1.5) has focal length 20cm in air. If it is immersed in a liquid of refractive index 1.60, its focal length will be:- a)100cm
- b)160cm
- c)-80cm
- d)-160cm
Correct answer is option 'D'. Can you explain this answer?
A convergent lens made of crown glass (refractive index 1.5) has focal length 20cm in air. If it is immersed in a liquid of refractive index 1.60, its focal length will be:
a)
100cm
b)
160cm
c)
-80cm
d)
-160cm
|
Mira Sharma answered |
When the lens is in air, we have (from lens maker's equation), 1/20 = [(1.5/1) - 1) (1/R1- 1/R2).
We are not bothered about the signs of R1 and R2 since they are unknown quantities.
Even though we know that the convergent lens will become divergent in the denser medium, we write lens maker's equation without bothering about the sign of its unknown focal length in the liquid. If if is the focal length in the liquid, we can write,
1/f = ((1.5/1.6) - 1) (1/R1 - 1/R2).
Dividing the first equation by the second, we obtain f/20 = 0.5x1.6/(-0.1) from which f = -160 cm
If two thin lenses of power p1 and p2 are held in contact then the power of the combination will be- a)p1 +p2
- b)p12 +p22
- c)p1 -p2
- d)(p1 +p2)1/2
Correct answer is option 'A'. Can you explain this answer?
If two thin lenses of power p1 and p2 are held in contact then the power of the combination will be
a)
p1 +p2
b)
p12 +p22
c)
p1 -p2
d)
(p1 +p2)1/2
|
Raghavendra Rane answered |
Explanation:
When two thin lenses of power p1 and p2 are held in contact, the power of the combination can be calculated using the lens formula:
1/f = 1/f1 + 1/f2
where f is the focal length of the combination lens, f1 is the focal length of the first lens, and f2 is the focal length of the second lens.
Using the relation p = 1/f, we get:
p = p1 + p2
This means that the power of the combination lens is equal to the sum of the powers of the individual lenses.
Therefore, the correct option is 'A' i.e. p1p2.
Summary:
When two thin lenses are held in contact, the power of the combination is equal to the sum of the powers of the individual lenses.
When two thin lenses of power p1 and p2 are held in contact, the power of the combination can be calculated using the lens formula:
1/f = 1/f1 + 1/f2
where f is the focal length of the combination lens, f1 is the focal length of the first lens, and f2 is the focal length of the second lens.
Using the relation p = 1/f, we get:
p = p1 + p2
This means that the power of the combination lens is equal to the sum of the powers of the individual lenses.
Therefore, the correct option is 'A' i.e. p1p2.
Summary:
When two thin lenses are held in contact, the power of the combination is equal to the sum of the powers of the individual lenses.
What is the unit of power of lens?- a)Centimetre
- b)Dioptre
- c)Metres
- d)Radians
Correct answer is option 'B'. Can you explain this answer?
What is the unit of power of lens?
a)
Centimetre
b)
Dioptre
c)
Metres
d)
Radians
|
|
Sandy Naaz answered |
Dioptre is unit of power..
1 dioptre =- a)1m-9
- b)1m-2
- c)1m-6
- d)1m-1
Correct answer is option 'D'. Can you explain this answer?
1 dioptre =
a)
1m-9
b)
1m-2
c)
1m-6
d)
1m-1
|
|
Anand Kumar answered |
Power=1/focal length
unit of power is dioptre or m^-1
unit of power is dioptre or m^-1
A concave lens of glass, refractive index 1.5, has both surfaces of same radius of curvature R. On immersion in a medium of refractive index 1.75, it will behave as a:- a)convergent lens of focal length 3.5R
- b)divergent lens of focal length 3.5R
- c)divergent lens of focal length 3.0R
- d)convergent lens of focal length 3.0R
Correct answer is option 'A'. Can you explain this answer?
A concave lens of glass, refractive index 1.5, has both surfaces of same radius of curvature R. On immersion in a medium of refractive index 1.75, it will behave as a:
a)
convergent lens of focal length 3.5R
b)
divergent lens of focal length 3.5R
c)
divergent lens of focal length 3.0R
d)
convergent lens of focal length 3.0R
|
Arjun Singhania answered |
A double convex thin lens made of glass of refractive index 1.6 has radii of curvature 15 cm each. The focal length of this lens when immersed in a fluid of refractive index 1.63 is
- a)– 407 cm
- b)125 cm
- c)25 cm
- d)+ 250 cm
Correct answer is option 'A'. Can you explain this answer?
A double convex thin lens made of glass of refractive index 1.6 has radii of curvature 15 cm each. The focal length of this lens when immersed in a fluid of refractive index 1.63 is
a)
– 407 cm
b)
125 cm
c)
25 cm
d)
+ 250 cm
|
|
Rajesh Khatri answered |
If two thin lenses of focal length f1 and f2 are held in contact then the focal length of the combination will be - a)
- b)
- c)
- d)none
Correct answer is option 'C'. Can you explain this answer?
If two thin lenses of focal length f1 and f2 are held in contact then the focal length of the combination will be
a)
b)
c)
d)
none
|
|
Khushi Pandey answered |
Option C is correct as..
1/f = 1/f1 + 1/f2
and,
P = P1 + P2
1/f = 1/f1 + 1/f2
and,
P = P1 + P2
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