Ray Optics: JEE Main Previous Year Questions (2021-2026)

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JEE Main Previous Year Questions (2021-2026): 
Ray Optics  
 
(January 2026) 
 
Q1: A biconvex lens is formed by using two thin planoconvex lenses, as shown in the 
figure. The refractive index and radius of curved surfaces are also mentioned in figure. 
When an object is placed on the left side of lens at a distance of 30 cm from the biconvex 
lens, the magnification of the image will be: 
 
(a) -2 
(b) -2.5 
(c) +2.5 
(d) +2 
Ans: (a) 
Sol:  
We use the Lens Maker's Formula for each planoconvex lens : 
 
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JEE Main Previous Year Questions (2021-2026): 
Ray Optics  
 
(January 2026) 
 
Q1: A biconvex lens is formed by using two thin planoconvex lenses, as shown in the 
figure. The refractive index and radius of curved surfaces are also mentioned in figure. 
When an object is placed on the left side of lens at a distance of 30 cm from the biconvex 
lens, the magnification of the image will be: 
 
(a) -2 
(b) -2.5 
(c) +2.5 
(d) +2 
Ans: (a) 
Sol:  
We use the Lens Maker's Formula for each planoconvex lens : 
 
 
For left Plano-convex lens (L
1
):  
The refractive index of the lens is µ
1
 = 1.5  
Radii of curvatures are R
1
 = 15 cm (curved surface), R
2
 = 8 (plane surface) 
 
For right Plano-convex lens (L
2
):  
The refractive index of lens µ
2
 = 1.2  
Radii of curvatures are R
1
 = 8 , (Plane surface) and R
2
 = - 12 cm (curved surface) 
 
Since the lenses are thin and in contact, the total power is the sum of individual powers : 
Page 3


JEE Main Previous Year Questions (2021-2026): 
Ray Optics  
 
(January 2026) 
 
Q1: A biconvex lens is formed by using two thin planoconvex lenses, as shown in the 
figure. The refractive index and radius of curved surfaces are also mentioned in figure. 
When an object is placed on the left side of lens at a distance of 30 cm from the biconvex 
lens, the magnification of the image will be: 
 
(a) -2 
(b) -2.5 
(c) +2.5 
(d) +2 
Ans: (a) 
Sol:  
We use the Lens Maker's Formula for each planoconvex lens : 
 
 
For left Plano-convex lens (L
1
):  
The refractive index of the lens is µ
1
 = 1.5  
Radii of curvatures are R
1
 = 15 cm (curved surface), R
2
 = 8 (plane surface) 
 
For right Plano-convex lens (L
2
):  
The refractive index of lens µ
2
 = 1.2  
Radii of curvatures are R
1
 = 8 , (Plane surface) and R
2
 = - 12 cm (curved surface) 
 
Since the lenses are thin and in contact, the total power is the sum of individual powers : 
 
Given object distance u = - 30 cm  
Using the Lens Formula: 
 
Magnification for a lens is given by : m = v/u 
 
The negative sign indicates that the image is real and inverted, and its size is twice the size of 
the object.  
Hence, the correct option is (a). 
 
Q2: For a transparent prism, if the angle of minimum deviation is equal to its refracting 
angle, the refractive index n of the prism satisfies. (a) n = 2  
(b) 2 < n < 2  
(c) 1 < n < 2  
(d) 2 < n < 2v2  
Ans: (b) 
Sol: 
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JEE Main Previous Year Questions (2021-2026): 
Ray Optics  
 
(January 2026) 
 
Q1: A biconvex lens is formed by using two thin planoconvex lenses, as shown in the 
figure. The refractive index and radius of curved surfaces are also mentioned in figure. 
When an object is placed on the left side of lens at a distance of 30 cm from the biconvex 
lens, the magnification of the image will be: 
 
(a) -2 
(b) -2.5 
(c) +2.5 
(d) +2 
Ans: (a) 
Sol:  
We use the Lens Maker's Formula for each planoconvex lens : 
 
 
For left Plano-convex lens (L
1
):  
The refractive index of the lens is µ
1
 = 1.5  
Radii of curvatures are R
1
 = 15 cm (curved surface), R
2
 = 8 (plane surface) 
 
For right Plano-convex lens (L
2
):  
The refractive index of lens µ
2
 = 1.2  
Radii of curvatures are R
1
 = 8 , (Plane surface) and R
2
 = - 12 cm (curved surface) 
 
Since the lenses are thin and in contact, the total power is the sum of individual powers : 
 
Given object distance u = - 30 cm  
Using the Lens Formula: 
 
Magnification for a lens is given by : m = v/u 
 
The negative sign indicates that the image is real and inverted, and its size is twice the size of 
the object.  
Hence, the correct option is (a). 
 
Q2: For a transparent prism, if the angle of minimum deviation is equal to its refracting 
angle, the refractive index n of the prism satisfies. (a) n = 2  
(b) 2 < n < 2  
(c) 1 < n < 2  
(d) 2 < n < 2v2  
Ans: (b) 
Sol: 
 
The refractive index n of a prism with refracting angle A and angle of minimum deviation d
m
 is 
given by the formula: 
 
According to question the angle of minimum deviation is equal to the refracting angle: 
 
The value of the refractive index depends on the possible values for the refracting angle A. 
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JEE Main Previous Year Questions (2021-2026): 
Ray Optics  
 
(January 2026) 
 
Q1: A biconvex lens is formed by using two thin planoconvex lenses, as shown in the 
figure. The refractive index and radius of curved surfaces are also mentioned in figure. 
When an object is placed on the left side of lens at a distance of 30 cm from the biconvex 
lens, the magnification of the image will be: 
 
(a) -2 
(b) -2.5 
(c) +2.5 
(d) +2 
Ans: (a) 
Sol:  
We use the Lens Maker's Formula for each planoconvex lens : 
 
 
For left Plano-convex lens (L
1
):  
The refractive index of the lens is µ
1
 = 1.5  
Radii of curvatures are R
1
 = 15 cm (curved surface), R
2
 = 8 (plane surface) 
 
For right Plano-convex lens (L
2
):  
The refractive index of lens µ
2
 = 1.2  
Radii of curvatures are R
1
 = 8 , (Plane surface) and R
2
 = - 12 cm (curved surface) 
 
Since the lenses are thin and in contact, the total power is the sum of individual powers : 
 
Given object distance u = - 30 cm  
Using the Lens Formula: 
 
Magnification for a lens is given by : m = v/u 
 
The negative sign indicates that the image is real and inverted, and its size is twice the size of 
the object.  
Hence, the correct option is (a). 
 
Q2: For a transparent prism, if the angle of minimum deviation is equal to its refracting 
angle, the refractive index n of the prism satisfies. (a) n = 2  
(b) 2 < n < 2  
(c) 1 < n < 2  
(d) 2 < n < 2v2  
Ans: (b) 
Sol: 
 
The refractive index n of a prism with refracting angle A and angle of minimum deviation d
m
 is 
given by the formula: 
 
According to question the angle of minimum deviation is equal to the refracting angle: 
 
The value of the refractive index depends on the possible values for the refracting angle A. 
As A approaches  
 
Therefore, n approaches 2 × 1 = 2.  
For minimum deviation to occur, the internal angle of incidence r = A/2 must be less than the 
critical angle C to let the light emerge from prism. 
 
This condition is satisfied for all A < 90
°
. 
 
For a practical transparent prism where 0 < A < 90
°
 , the refractive index must fall in the range:  
v2 < n < 2  
Hence, the correct option is (b). 
 
Q3: The magnitudes of power of a biconvex lens (refractive index 1.5) and that of a 
plano-concave lens (refractive index = 1.7) are same. If the curvature of planoconcave 
lens exactly matches with the curvature of back surface of the biconvex lens, then ratio 
of radius of curvature of front and back surface of the biconvex lens is ____  
(a) 2 : 5  
(b) 5 : 2  
(c) 12 : 5  
(d) 5 : 12 
Ans: (b) 
Sol:  
If the focal length of a lens is f (in meters) then its power is given as P = 1/f … (i)