DC Pandey Solutions: Reflection of Light

# DC Pandey Solutions: Reflection of Light | Physics Class 12 - NEET PDF Download

Introductory Exercise 27.1

Ques 1: Show that the unit of  is m/s.
Sol:
= Speed of light in vacuum.

Ques 2: The magnetic field in a plane electromagnetic wave is given by (SI units)
By = (2 × 10-7 T) sin [500 x + 1.5 × 1011 t]
(a) What is the wavelength and frequency of the wave?
(b) Write an expression for the electric field vector.
Ans:

= 0.0125 m= 1.25 cm

= 2.39 × 1010Hz

E0 = cB0
= (3 × 108)(2 × 10-7) = 60 V/m
kx and ωt have same sign. Therefore, electromagnetic wave is travelling along negative x direction.  are in mutually perpendicular direct ions. Hence oscillations  of are along z-direction.

Introductory Exercise 27.2

Ques 1: Prove that for any value of angle i, rays 1 and 2 are parallel.

Sol:

PQ and MN are mutually parallel. Rays 1 and 2 are making equal angles (= ∠i) from PQ and MN. So, they are mutually parallel.

Ques 2: A man approaches a vertical plane mirror at speed of 2 m/s. At what rate does he approach his image?
Sol:

Ques 3: A pole of height 4 m is kept in front of a vertical plane mirror of length 2 m. The lower end of the mirror is at a height of 6 m from the ground. The horizontal distance between the mirror and the pole is 2 m. Up to what minimum and maximum heights a man can see the image of top of the pole at a horizontal distance of 4 m (from the mirror) standing on the same horizontal line which is passing through the pole and the horizontal point below the mirror?
Sol:

PQ = Pole
MN = Image of pole

Further,

Maximum height required = AE = BE+ AB = 16 m

Introductory Exercise 27.3

Ques 1: Assume that a certain spherical mirror has a focal length of- 10.0 cm. Locate and describe the image for object distances of
(a) 25.0 cm (b) 10.0 cm (c) 5.0 cm.
Sol:
Apply
(a) f = -10 cm, u = - 25 cm Solving we get, v = -16.7cm
Since, v is negative, image is in front of mirror. So it is real. Similarly, we can solve for other parts.

Ques 2: A ball is dropped from rest 3.0 m directly above the vertex of a concave mirror that has a radius of 1.0 m and lies in a horizontal plane.
(a) Describe the motion of ball's image in the mirror.
(b) At what time do the ball and its image coincide?
Sol:
(a) From O to F, image is real.
From F to P, image is virtual.

At O

v = - 0.6 m

(b) When object is at C and P, image coincides with object. Using,

or

Ques 3: A spherical mirror is to be used to form on a screen 5.0 m from the object an image five times the size of the object.
(a) Describe the type of mirror required.
(b) Where should the mirror be positioned relative to the object?
Sol:
(a) Image has to be taken on a screen. So it should be real. Hence mirror should be concave.

Image is 5 times magnified. Hence, | v | = 5 | u |
or
(5 + x) = 5x
Solving we get, x = 1.25 cm
Now using,
We have,
Solving we get, R = - 2.08 m

Ques 4: Figure shows two rays P and Q being reflected by a mirror and going as F and Q'. State which type of mirror is this?

Sol:
Reflected rays are neither converging nor diverging. Hence, mirror is plane.

Ques 5: The following table shows object distance, object size, and mirror focal length (all in centimeters) for various situations. Use ray tracing to determine the image size and location for each case.

Sol:
Let us draw the ray diagram for the first part.

In ΔO1O2P and ΔP I1I2 we have,

or
x = (20)(I1,I2) ...(i)

In ΔO1O2C and l1I2 C we have,

or (40 - x) = 40(I1I2) ....(ii)
Solving Eqs. (i) and (ii) we get,

Ques 6: Complete the following table for spherical mirrors. All distances are in centrimeters.

 Mirror Type Radius Focal Length Object Distance Image Distance Lateral Magnification Real/Virtual Image -25 40 20 -30 +15 +30 20 -2.0 +20 -40 -10 +2.0

Sol: Negative focal length means concave mirror and positive focal length means convex mirror.
Apply,
And
Further, if v is negative then image is in front of mirror. So, it is real and inverted.
R = 2f

The document DC Pandey Solutions: Reflection of Light | Physics Class 12 - NEET is a part of the NEET Course Physics Class 12.
All you need of NEET at this link: NEET

## Physics Class 12

105 videos|425 docs|114 tests

## FAQs on DC Pandey Solutions: Reflection of Light - Physics Class 12 - NEET

 1. What is reflection of light?
Ans. Reflection of light is the phenomenon where light rays bounce off a surface and change direction. It occurs when light encounters a smooth and shiny surface, such as a mirror or a polished metal object. The angle at which the light rays strike the surface is equal to the angle at which they reflect off.
 2. How does reflection of light occur?
Ans. Reflection of light occurs due to the interaction between light rays and the molecules or atoms on the surface of an object. When light rays hit a surface, they are either absorbed by the material or reflected. The reflected light rays bounce off the surface and travel in a different direction, following the law of reflection.
 3. What is the law of reflection?
Ans. The law of reflection states that the angle of incidence (the angle at which the light ray strikes the surface) is equal to the angle of reflection (the angle at which the light ray bounces off the surface). This means that the incident ray, the normal (a line perpendicular to the surface), and the reflected ray all lie in the same plane.
 4. What are the types of reflection?
Ans. There are two types of reflection: regular reflection and diffuse reflection. Regular reflection occurs when light rays reflect off a smooth and polished surface, such as a mirror, at a specific angle. Diffuse reflection, on the other hand, occurs when light rays reflect off a rough or irregular surface, scattering in different directions.
 5. How is reflection of light used in everyday life?
Ans. Reflection of light is used in various everyday life applications. Some examples include: - Mirrors: Mirrors use regular reflection to produce clear and accurate reflections of objects. - Periscopes: Periscopes use multiple reflections to allow people to see objects around corners or over obstacles. - Solar panels: Solar panels use reflection to trap and redirect sunlight, converting it into electricity. - Traffic signs: Reflective materials used in traffic signs enhance their visibility at night by reflecting the light from car headlights.

## Physics Class 12

105 videos|425 docs|114 tests

### Up next

 Explore Courses for NEET exam

### How to Prepare for NEET

Read our guide to prepare for NEET which is created by Toppers & the best Teachers
Signup to see your scores go up within 7 days! Learn & Practice with 1000+ FREE Notes, Videos & Tests.
10M+ students study on EduRev
Related Searches

,

,

,

,

,

,

,

,

,

,

,

,

,

,

,

,

,

,

,

,

,

;