Question 11 Mark
Draw the following diagram in your answer-book and show the formation of image of the object AB with the help of suitable rays.
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Question 21 Mark
What is the magnification of the images formed by plane mirrors and why?
Answer
View full question & answer→The magnification of the image formed by a plane mirror is 1. This is because the size of the image formed is equal to the size of the object.
Magnification, $m = \frac{H_{i}}{H_{o}} = 1 \ \ \ \ \ \ \ (H = H_{o})$
Here, $H_{i}$ is the height of the image and $H_{o}$ is the height of the object.
Magnification, $m = \frac{H_{i}}{H_{o}} = 1 \ \ \ \ \ \ \ (H = H_{o})$
Here, $H_{i}$ is the height of the image and $H_{o}$ is the height of the object.
Question 31 Mark
What is meant by power of a lens?
Answer
View full question & answer→Power of a lens- The degree of convergence or divergence of light rays achieved by a lens/Reciprocal of focal length of a lens.
Question 41 Mark
Explain why a ray of light passing through the centre of curvature of a concave mirror gets reflected along the same path.
Answer
View full question & answer→This is because the angle of incidence is $0^0$ that is the ray passing through the centre of curvature is incident normally to the mirror. The angle of reflection should also be $0^0$.
Question 51 Mark
What is the nature of the image formed by a concave mirror if the magnification produced by the mirror is + 3?
Answer
View full question & answer→The magnification has a plus sign then the image is virtual and erect. Here the magnification is greater than 1 therefore the image will be formed is larger than the object.
Question 61 Mark
Why does a ray of light bend when it travels from one medium into another?
Answer
View full question & answer→The refraction of light (bending of light ray) depends upon the change in speed of light. If speed of light changes so it will bend when travelling from one medium to another.
Question 71 Mark
Draw the given diagram in your answer book and complete it for the path of ray of light beyond the lens.
Question 81 Mark
The refractive index of diamond is 2.42. What is the meaning of this statement in relation to speed of light?
Answer
View full question & answer→The refractive index of diamond is 2.42. This means that the speed of light in diamond will reduce by a factor of 2.42 as compared to its speed in air.
Question 91 Mark
Copy this figure in your answer-book and show the direction of the light ray after reflection:
Question 101 Mark
The magnification produced by a plane mirror is +1. What does this mean?
Answer
View full question & answer→$\text{m}=\frac{\text{h}_\text{i}}{\text{h}_\text{0}} = \frac{\text{v}}{\text{u}}$Magnification produced by a plane mirror is +1 which means that size of image formed is exactly equal to size of object behind the mirror.
Question 111 Mark
Draw a labelled ray diagram to show the formation of image in a convex mirror when the object is at infinity. Mark clearly the pole and focus of the mirror in the diagram.
Answer
View full question & answer→Coming Soon
Question 121 Mark
The image seen in a plane mirror cannot be formed on a screen. What name is given to this type of image?
Answer
View full question & answer→Virtual image.
Question 131 Mark
What sign (+ve or -ve) has been given to the following on the basis of Cartesian Sign Convention?
- Height of a real image.
- Height of a virtual image.
Answer
View full question & answer→- Negative.
- Positive.
Question 141 Mark
What kind of mirrors are used in big shopping centres to watch the activities of the customers?
Answer
View full question & answer→Convex mirrors.
Question 151 Mark
State one use of concave mirror based on the formation of image as in case (z) above.
Answer
View full question & answer→one use of concave mirror based on the formation of image as in case (i) above: As a shaving mirror.
Question 161 Mark
Define:principal axis.
Answer
View full question & answer→Principal axis: The straight line passing through the centre of curvature and pole of a spherical mirror is called its principal axis.
Question 171 Mark
A beam of light travelling in a rectangular glass slab emerges into air. Draw a ray-diagram indicating the change in its path.
Answer
View full question & answer→A ray of light travelling from the glass slabs and emerges into the air.
Question 181 Mark
A ray of light goes from water into air. Will it bend towards the normal or away from the normal?
Answer
View full question & answer→It will bend away from the normal.
Question 191 Mark
Which of the two has a greater power:
A lens of short focal length or a lens of large focal length?
A lens of short focal length or a lens of large focal length?
Answer
View full question & answer→Lens of short focal length.
Question 201 Mark
What is inverted image?
Answer
View full question & answer→An image in which up and down, as well as left and right, are interchanged, that is, an image that results from rotating the object 180° about a line from the object to the observer, such images are formed by most astronomical telescopes. Also known as reversed image.
Question 211 Mark
What type of image/ images are formed by:
- A convex mirror?
- A concave mirror?
Answer
View full question & answer→- Virtual and erect.
- Virtual and erect; real and inverted.
Question 221 Mark
Where should an object be placed in front of a convex lens so as to obtain its real, inverted and magnified image?
Answer
View full question & answer→Object should be placed between f and 2f.
Question 231 Mark
If you want to see an enlarged image of your face, state whether you will use a concave mirror or a convex mirror?
Answer
View full question & answer→Concave mirror.
Question 241 Mark
Which type of mirror has:
- Positive focal length?
- Negative focal length?
Answer
View full question & answer→- Convex mirror.
- Concave mirror.
Question 251 Mark
According to the “New Cartesian Sign Convention” for mirrors, what sign has been given to the focal length of:
- A concave mirror?
- A convex mirror ?
Answer
View full question & answer→- Negative.
- Positive.
Question 261 Mark
Which one of these circumstances enables a concave mirror to be used as a shaving mirror?
Answer
View full question & answer→A concave mirror can be used as a shaving mirror when the object is placed between the pole and focus of a concav mirror.
Question 271 Mark
What is meant by the refractive index of a substance?
Answer
View full question & answer→Refractive index of substance: The ratio of speed of light in vacuum to the speed of light in a medium, is calles the refractive index of that medium.
Question 281 Mark
For what position of an object, a real and diminished image is formed by a concave mirror?
Answer
View full question & answer→Beyond the centre of curvature.
Question 291 Mark
What name is given to the ratio of sine of angle of incidence to the sine of angle of refraction?
Answer
View full question & answer→Refractive index.
Question 301 Mark
Why do we not see the actual depth of a lake?
Answer
View full question & answer→Because of Refraction, its due to apparent shift.
Question 311 Mark
A 50cm tall object is at a very large distance from a diverging lens. A virtual, erect and diminished image of the object is formed at a distance of 20cm in front of the lens. How much is the focal length of the lens?
Answer
View full question & answer→When an object is placed at a very large distance from a diverging lens, then image is formed at the focus of the lens. Therefore, the focal length of the lens is 20cm.
Question 321 Mark
What is the nature of a lens whose power is, -4D?
Answer
View full question & answer→Concave lens.
Question 331 Mark
Write the relation between the angle of incidence and the angle of refraction for a medium.
Answer
View full question & answer→$\text{Refractive index} = \frac{\text{sine of the angle of incidence}}{\text{sine of the angle of refraction}}$
Question 341 Mark
What kind of mirror can have a focal length of, – 20cm?
Answer
View full question & answer→Concave mirror (since focal length is negative).
Question 351 Mark
State three characteristics of the image formed in this case.
Answer
View full question & answer→Coming Soon
Question 361 Mark
The focal length of a convex lens is 25cm. What is its power?
Answer
View full question & answer→$\text{f}=25\text{cm}=0.25\text{cm}$$\text{p}=\frac{1}{\text{f}}=\frac{1}{0.25}=+4\text{D}$
Question 371 Mark
Where should an object be placed in front of a convex lens so as to obtain its virtual, erect and magnified image?
Answer
View full question & answer→The object should be placed within focus.
Question 381 Mark
An object is placed at a long distance in front of a convex mirror of radius of curvature 30cm. State the position of its image.
Answer
View full question & answer→Image is formed at the focus.$\text{focus}=\frac{30}{2}=15\text{cm}$
Exmpale: 15cm behind the convex mirror.
Exmpale: 15cm behind the convex mirror.
Question 391 Mark
What type of image is formed:
- In a plane mirror?
- On a cinema screen?
Answer
View full question & answer→- Virtual image.
- Real image.
Question 401 Mark
What is the ratio of the height of an image to the height of an object known as?
Answer
View full question & answer→The ratio of the height of an image to the height of an object known as magnifincation.
Question 411 Mark
If an object is placed at the focus of a convex lens, where is the image formed?
Answer
View full question & answer→The image is formed at infinity (at very large distance).
Question 421 Mark
Name the mirror which can give:
- An erect and enlarged image of an object.
- An erect and diminished image of an object.
Answer
View full question & answer→- Concave mirror.
- Convex mirror.
Question 431 Mark
A 1cm high object is placed at a distance of 2f from a convex lens. What is the height of the image formed?
Answer
View full question & answer→1cm (same as the height of the object).
Question 441 Mark
A ray of light travelling in water emerges into air. Draw a ray-diagram indicating the change in its path.
Answer
View full question & answer→A ray of light travelling through water to air.
Question 451 Mark
Describe the nature of image formed when an object is placed at a distance of 30cm from a convex lens of focal length 15cm.
Answer
View full question & answer→Since the object is placed at a distance greater than the focal length of the convex lens, so the image formed is real and inverted.
Question 461 Mark
A ray of light travelling in air is incident on a parallel-sided glass slab (or rectangular glass slab). Draw a ray-diagram indicating the change in its path in glass.
Answer
View full question & answer→A ray of light incidence on parallel sided glass slab.
Question 471 Mark
Name the spherical mirror which can produce a real and diminished image of an object.
Answer
View full question & answer→Concave mirror.
Question 481 Mark
If the image formed by a convex lens is of the same size as that of the object, what is the position of the image with respect to the lens?
Answer
View full question & answer→At 2F (At twice the focal length).
Question 491 Mark
Name a mirror that can give an erect and enlarged image of an object.
Answer
View full question & answer→Only a concave mirror can give a erect and enlarged image of an object.
Question 501 Mark
What is the power of a convex lens whose focal length is 80cm?
Answer
View full question & answer→$\text{f}=80\text{cm}=0.08\text{m}$$\text{p}=\frac{1}{\text{f}}=\frac{1}{0.08}=+1.25\text{D}$