Ray Optics · JEE Main previous year questions

The distance between object and its two times magnified real image as produced by a convex lens is $45\text{ cm}$. The focal length of the lens used is _________ cm.

A convex mirror of radius of curvature $30\text{ cm}$ forms an image that is half the size of the object. The object distance is :

1. A.$-45\text{ cm}$
2. B.$-15\text{ cm}$
3. C.$45\text{ cm}$
4. D.$15\text{ cm}$

A biconvex lens of refractive index $1.5$ has a focal length of $20\text{ cm}$ in air. Its focal length when immersed in a liquid of refractive index $1.6$ will be:

1. A.$-16\text{ cm}$
2. B.$+16\text{ cm}$
3. C.$+160\text{ cm}$
4. D.$-160\text{ cm}$

If the distance between object and its two times magnified virtual image produced by a curved mirror is $15\text{ cm}$, the focal length of the mirror must be:

1. A.$-10\text{ cm}$
2. B.$-12\text{ cm}$
3. C.$15\text{ cm}$
4. D.$10/3\text{ cm}$

If the refractive index of the material of a prism is $\cot \left(\frac{A}{2}\right)$, where $A$ is the angle of prism then the angle of minimum deviation will be

1. A.$\pi -2A$
2. B.$\frac{\pi }{2}-2A$
3. C.$\pi -A$
4. D.$\frac{\pi }{2}-A$

A convex lens of focal length $40\text{ cm}$ forms an image of an extended source of light on a photoelectric cell. A current I is produced. The lens is replaced by another convex lens having the same diameter but focal length $20\text{ cm}$. The photoelectric current now is :

1. A.$\frac{I}{2}$
2. B.$4\text{ I}$
3. C.$2\text{ I}$
4. D.$I$

An object is placed in a medium of refractive index $3$ . An electromagnetic wave of intensity $6\times 10^8{\text{ W/m}}^2$ falls normally on the object and it is absorbed completely. The radiation pressure on the object would be (speed of light in free space $=3\times 10^8\text{ m/s}$ ) :

1. A.$6{\text{ Nm}}^{-2}$
2. B.$36{\text{ Nm}}^{-2}$
3. C.$18{\text{ Nm}}^{-2}$
4. D.$2{\text{ Nm}}^{-2}$

A vessel of depth '$d$' is half filled with oil of refractive index $n_1$ and the other half is filled with water of refractive index $n_2$. The apparent depth of this vessel when viewed from above will be-

1. A.$\frac{2d(n_1+n_2)}{n_1{n}_2}$
2. B.$\frac{d(n_1+n_2)}{2n_1{n}_2}$
3. C.$\frac{d{n}_1{n}_2}{2(n_1+n_2)}$
4. D.$\frac{d{n}_1{n}_2}{(n_1+n_2)}$

A fish rising vertically upward with a uniform velocity of $8{\text{ ms}}^{-1}$, observes that a bird is diving vertically downward towards the fish with the velocity of $12{\text{ ms}}^{-1}$. If the refractive index of water is $\frac{4}{3}$, then the actual velocity of the diving bird to pick the fish, will be _________ ${\text{ms}}^{-1}$.

A bi convex lens of focal length $10\text{ cm}$ is cut in two identical parts along a plane perpendicular to the principal axis. The power of each lens after cut is ___________ D.

Two convex lenses of focal length $20\text{ cm}$ each are placed coaxially with a separation of $60\text{ cm}$ between them. The image of the distant object formed by the combination is at _________ $\text{cm}$ from the first lens.

The critical angle for a denser-rarer interface is $45^{\circ }$. The speed of light in rarer medium is $3\times 10^8\text{ m/s}$. The speed of light in the denser medium is:

1. A.$2.12\times 10^8\text{ m/s}$
2. B.$5\times 10^7\text{ m/s}$
3. C.$\sqrt{2}\times 10^8\text{ m/s}$
4. D.$3.12\times 10^7\text{ m/s}$

The radius of curvature of each surface of a convex lens having refractive index 1.8 is $20\text{ cm}$. The lens is now immersed in a liquid of refractive index 1.5. The ratio of power of lens in air to its power in the liquid will be $x:1$. The value of $x$ is _________.

When one light ray is reflected from a plane mirror with $30^{\circ }$ angle of reflection, the angle of deviation of the ray after reflection is :

1. A.$140^{\circ }$
2. B.$130^{\circ }$
3. C.$120^{\circ }$
4. D.$110^{\circ }$

An object is placed at a distance of 12 cm in front of a plane mirror. The virtual and erect image is formed by the mirror. Now the mirror is moved by 4 cm towards the stationary object. The distance by which the position of image would be shifted, will be

1. A.4 cm towards mirror
2. B.2 cm towards mirror
3. C.8 cm away from mirror
4. D.8 cm towards mirror

In a reflecting telescope, a secondary mirror is used to:

1. A.make chromatic aberration zero
2. B.remove spherical aberration
3. C.reduce the problem of mechanical support
4. D.move the eyepiece outside the telescopic tube

Two transparent media having refractive indices $1.0$ and $1.5$ are separated by a spherical refracting surface of radius of curvature $30\mathrm{cm}$. The centre of curvature of surface is towards denser medium and a point object is placed on the principal axis in rarer medium at a distance of $15\mathrm{cm}$ from the pole of the surface. The distance of image from the pole of the surface is ____ $\mathrm{cm}$.

A monochromatic light wave with wavelength ${\lambda }_1$ and frequency $v_1$ in air enters another medium. If the angle of incidence and angle of refraction at the interface are $45^{\circ }$ and $30^{\circ }$ respectively, then the wavelength ${\lambda }_2$ and frequency $v_2$ of the refracted wave are:

1. A.${\lambda }_2={\lambda }_1,v_2=\frac{1}{\sqrt{2}}{v}_1$
2. B.${\lambda }_2={\lambda }_1,v_2=\sqrt{2}{v}_1$
3. C.${\lambda }_2=\sqrt{2}{\lambda }_1,v_2=v_1$
4. D.${\lambda }_2=\frac{1}{\sqrt{2}}{\lambda }_1,v_2=v_1$

Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R Assertion A: The phase difference of two light waves changes if they travel through different media having same thickness, but different indices of refraction. Reason R: The wavelengths of waves are different in different media. In the light of the above statements, choose the most appropriate answer from the options given below

1. A.Both A and R are correct but R is NOT the correct explanation of A
2. B.A is correct but R is not correct
3. C.A is not correct but R is correct
4. D.Both A and R are correct and R is the correct explanation of A

A thin cylindrical rod of length $10\text{ cm}$ is placed horizontally on the principal axis of a concave mirror of focal length $20\text{ cm}$. The rod is placed in such a way that mid point of the rod is at $40\text{ cm}$ from the pole of mirror. The length of the image formed by the mirror will be $\frac{x}{3}\text{ cm}$. The value of $x$ is ________.

A microscope is focused on an object at the bottom of a bucket. If liquid with refractive index $\frac{5}{3}$ is poured inside the bucket, then the microscope has to be raised by $30\text{ cm}$ to focus the object again. The height of the liquid in the bucket is :

1. A.$50\text{ cm}$
2. B.$18\text{ cm}$
3. C.$75\text{ cm}$
4. D.$12\text{ cm}$