Question

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Answer 1

Answer:

1 a.incident ray ,reflected ray and normal all lie in the same plane.

b.angle of incidence is equal to the angle of reflection

2. 40 degree

3. 9 cm

4. upright,of same size as the object ,erect

5. 50 degree.angle of incidence =angle of reflection.

6. Periscope , kaleidoscope

7 Regular reflection occurs at the surface of a plane surface like a plane mirror. Reflected rays after regular reflection are parallel. Diffused reflection occurs at the surface of a rough surface like cardboard. Reflected rays after regular reflection are not parallel.

8. 3 images are formed when two mirrors are placed parallel to each other. 60 degeree=360/60 = 6-1=5 images.

Answer 2

$\sf { _!! Question !_! }$

State the laws of reflection along with diagram.

$\sf { _!! Answer !_! }$

$\implies$ Laws of reflection-

• The incident ray, the reflected ray and the normal at the point of incidence lie on the same plane.

• The angle of incidence is always equal to rhe angle of reflection.

[ Refer to the attachment for the diagram. ]

$\sf { _!! Question !_! }$

A ray of light incident on a plane mirror forms an angle of 40° with the mirror. What is the angle of reflection?

$\sf { _!! Answer !_! }$

$\implies$ The angle of reflection will be 40° because angle of reflection is always equal to the angle of reflection.

$\sf { _!! Question !_! }$

The distance between the object and its image formed by a plane mirror appears to be 18cm. What is the distance between the mirror and the object?

$\sf { _!! Answer !_! }$

$\implies$ 9 cm is the distance between the mirror and the object.

$\sf { _!! Question !_! }$

Draw a ray diagram to show the image formed by a plane mirror. Also list the characteristics of the image formed by a plane mirror.

$\sf { _!! Answer !_! }$

$\implies$ Characteristics of the images formed by a plane mirror-

• laterally inverted

• virtual and erect

• of the same size as the object

• the image is formed as far behind the mirror as the object in front of it.

[ Refer to the attachment for the diagram. ]

$\sf { _!! Question !_! }$

The angle between the incident ray and reflected ray is 100°. What is the value of angle of incidence? How did you arrive at your answer?

$\sf { _!! Answer !_! }$

$\implies$ The value of angle of incidence is 50°. We know that the angle of incidence and angle of reflection is always equal. We are given that The angle between the incident ray and reflected ray is 100°. It means 100/2 will be equal to the both angle of reflection and angle of incidence which is equal to 50°.

$\sf { _!! Question !_! }$

Name two devices that use multiple reflections.

$\sf { _!! Answer !_! }$

$\implies$ Kaleidoscope and periscope.

$\sf { _!! Question !_! }$

Differentiate between regular reflection and diffused reflection.

$\sf { _!! Answer !_! }$

$\implies$ Regular reflection- When a parallel beam of light falls on a surface and reflected back as a parallel beam in one particular direction, then it is called regular reflection.

Diffused reflection- When a parallel beam of light falls upon a surface and reflects back unparallely then it is called diffused reflection.

$\sf { _!! Question !_! }$

How many images will formed when two mirrors are placed parallel to each other? How does it change when the two mirrors are placed adjacent to each other at an angle of 60°.

$\sf { _!! Answer !_! }$

$\implies$ There will be formed infinite images when two mirrors are placed parallel to each other.

But when two mirrors are placed adjacent to each other at an angle of 60°, 5 images will be formed.

$\rm { No. \: of \: images = \dfrac{360°}{Angle \: b/w \: mirrors} -1 }$

$\rm { No. \: of \: images \: formed = \cancel { \dfrac{360°}{60 }} -1 }$

$\rm { No. \: of \: images \: formed = 6 - 1 = 5 \: images }$

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