Ray Optics (9 Dec) - Live Session - NEET 2020Contact Number: 9667591930 / 8527521718

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A convex mirror of focal length *f* produces an image (1/n)^{th} of the size of the object. Then the distance of

the object from the mirror is

(1) $\frac{n}{f}$

(2) $\frac{n+1}{f}$

(3) $\frac{n}{f-1}$

(4) (n-1) f

An equilateral prism is kept as shown in the figure. A ray *PQ* is incident on one of the faces. For the

minimum deviation of the incident ray,

(1)* PQ* must be horizontal

(2)* QR* must be horizontal

(3)*RS* must be horizontal

(4) any one of them may be horizontal

A thin, symmetric double-convex lens of power *P* is cut into three parts *A*, *B* and *C* as shown. The power of

(1) *A* is *P/2 *

(2) *A *is 2*P*

(3) *B* is *P*/2

(4) *B *is *P*/4

An air bubble in glass slab ($\mu $ = 1.5) when viewed from one side appears to be at 6 cm and from opposite side 4 cm. The thickness of glass slab is

(1) 10 cm

(2) 6.67 cm

(3) 15 cm

(4) none of these

Two thin lenses, one concave and the other convex are placed in contact with each other. If their powers are in

the ratio 2 / 3 and the effective focal length of the combination is 30 cm, then the individual focal lengths are

(1) –75 cm, +50 cm

(2) –15cm, 10 cm

(3) +75 cm, –50cm

(4) 75 cm, 50 cm

There is an equiconvex glass lens with radius of each face as *R* and _{${}_{a}\mu _{g}$} = 3/2 and _{${}_{a}\mu _{w}$} = 4/3. If there is water in object space and air in image space, then the focal length is

(1) 2*R*

(2) *R*

(3) 3*R*/2

(4) 3 *R*

The plane face of plano-convex lens of focal length 20 cm is silvered. The type of mirror and focal length is

(1) convex, *f* = 20 cm

(2) concave, *f* = 20 cm

(3) convex, *f* = 10 cm

(4) concave, *f* = 10 cm

The diagrams show lenses which either equiconvex or plano convex. All curvatures are the same and the

glass of all the lenses are identical. What are the relative magnitudes of the resultant focal lengths of the

lenses arranged as shown* P Q R *

(1) 1 1 1

(2) 1 1 –1

(3) 2 1 1

(4) 2 1 –1

A thin lens of focal length *f* produces an upright image of the same size as the object. What is the distance of

the object from the optical centre of the lens?

(1) 2 *f*

(2) zero

(3) 3*f* /2

(4) infinity

A ray of light is incident normally on one of the faces of a prism of apex angle 30^{$\xb0$} and refractive index $\sqrt{2}$.

The angle of deviation of the ray in degree is

(1) 15

(2) 30

(3) 45

(4) 60

A diver in a swimming pool wants to signal his distress to a person lying on the edge of the pool by flashing his waterproof flash light:

(1) he must direct the beam vertically upwards.

(2) he has to direct the beam horizontally.

(3) he has to direct the beam at an angle to the vertical which is slightly less than the critical angle of incidence for total internal reflection.

(4) he has to direct the beam at an angle to the vertical which is slightly more than the critical angle of incidence for internal reflection.

A concave mirror of focal length *f* (in air) is immersed in water ($\mu $ = 4/3). The focal length of mirror in water will be

(1) *f*

(2) $\frac{4}{3}f$

(3) $\frac{3}{4}f$

(4) $\frac{7}{3}f$

Two lenses of power 6D and –2D are combined to form a single lens. The focal length of this lens will be:

(1) $\frac{3}{2}m$

(2) $\frac{1}{4}m$

(3) 4 m

(4) $\frac{1}{8}m$

Angle of minimum deviation is equal to the angle of prism *A* of an equilateral glass prism. The angle

of incidence at which minimum deviation will be obtained is:

(1) 60°

(2) 30°

(3) 45°

(4)${\mathrm{sin}}^{-1}\left(\frac{2}{3}\right)$

When a ray of light enters a glass slab from air

(1) its wavelength decreases

(2) its wavelength increases

(3) its frequency increases

(4) neither wavelength increases nor frequency changes

A thin convergent glass lens ($\mu $_{g} = 1.5) has a power of + 5.0 D. When this lens is immersed in a liquid of refractive index $\mu $_{1} it acts as a divergent lens of focal length 100 cm. The value of $\mu $_{1} must be

(1) 4/3

(2) 5/3

(3) 2

(4) 7/3

A ray of light travels in the fashion as shown in the figure. After passing through water, the ray grazes along the water

air interface. The value of $\mu $_{g} in terms of *i* is:

(1) $\frac{1}{\mathrm{sin}i}$

(2) $\frac{3}{4\mathrm{sin}i}$

(3) $\frac{4}{3\mathrm{sin}i}$

(4) none of the above

A ray of light passes from vacuum into a medium of refractive index $\mu $, the angle of incidence is found to be

twice the angle of refraction. Then the angle of incidence is

(1) ${\mathrm{cos}}^{-1}\left(\frac{\mu}{2}\right)$ (2) $2{\mathrm{cos}}^{-1}\left(\frac{\mu}{2}\right)$

(3) $2{\mathrm{sin}}^{-1}\left(\mu \right)$ (4)

A thin plano-convex lens of focal length 15 cm has its plane side silvered. An object is placed on the principal

axis of the lens at a distance 20 cm from it as shown. The final position of the image is

(1) 60 cm to the right of the lens

(2) 60 cm to the left of the lens

(3) 30 cm to the left of the lens

(4) 12 cm to the left of the lens

A glass prism of refractive index 1.5 is immersed in water ($\mu $ = 4/3). Light beam incident normally on the face *AB* is totally reflected to reach the face *BC* if

(1) sin$\theta $ > 8/9

(2) 2/3 < sin$\theta $ < 8/9

(3) sin $\theta $ $\le $ 2/3

(4) cos $\theta $ $\ge $ 8/9

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