In this page, we are providing Light Class 7 Extra Questions and Answers Science Chapter 15 pdf download. NCERT Extra Questions for Class 7 Science Chapter 15 Light with Answers will help to score more marks in your CBSE Board Exams.
Class 7 Science Chapter 15 Extra Questions and Answers Light
Extra Questions for Class 7 Science Chapter 15 Light with Answers Solutions
Light Class 7 Extra Questions Very Short Answer Type
What type of mirror is used as a side view mirror in a scooter?
How can we change the direction of the light?
We can change the direction of the light by phenomenon called reflection.
What happens when a beam of light enters a prism?
The beam of light splits into seven colours.
Define briefly a convex mirror.
A mirror which reflects the light from its inner polished side is a convex mirror.
When we see an ambulance we see that the letters which actually appears to right is seen by us on left side. What is this effect called?
This effect is called lateral inversion.
What is virtual image?
The image which cannot be obtained on a screen is called a virtual image.
What is a lens?
A lens is a piece of refracting transparent medium bounded by two surfaces in which at least one has curved surface.
Name the two type of lenses.
- Concave lens
- Convex lens.
What kind of image is formed by concave lens?
A concave lens always forms erect, virtual and smaller image than the object.
What is prism?
The transparent glass pyramid bounded by four triangular surfaces that separate white light into spectrum of colours is called prism.
What are spherical mirrors?
The mirrors which have curved surface are known as spherical mirror.
Light Class 7 Extra Questions Short Answer Type
What is regular reflection?
When parallel rays of light fall on a smooth or polished surface, the reflected rays are parallel to each other. This is called regular reflection.
List two uses of concave mirror.
Following are two uses of concave mirror:
(i) It is used by dentists and doctors.
(ii) Concave mirrors are used in head lights of the cars, buses, shaving mirror, etc.
What is the kind of image formed by a concave mirror?
Concave mirror forms real and inverted image but when the object is placed very near to the mirror then the image formed to be virtual erect and magnified.
List two uses of convex mirror.
Answer:Following are the two uses of convex mirror:
(i) It is used as a side view mirror to help the drivers to see the traffic behind them.
(ii) It is used in shops, parking lots, etc., to get larger view of the area.
State any two uses of convex lens.
(i) It is used as a magnifying glass in hand lenses, microscope, telescope, etc.
(ii) It is used in spectacles to correct far-sightedness.
What is light?
Light is a form of electromagnetic radiation (radiation energy) which produces in us the sensation of vision. Light travels along a straight line.
What are the characteristics of image formed by a convex mirror?
Following are the characteristics of image formed by a convex mirror:
- Image is erect.
- The image is smaller than the object.
- The image formed is virtual.
Light Class 7 Extra Questions Long Answer Type
Differentiate between the following:
(a) Convex mirror and convex lens
(b) Concave mirror and concave lens
(c) Convex mirror and concave mirror
|Convex mirror||Convex lens|
|(i) It is opaque.||(i) It is transparent.|
|(ii) It causes reflection of light.||(ii) It cause refraction of light.|
|(iii) It forms only virtual, erect and diminished image.||(iii) It forms real, inverted, virtual, erect and magnified image.|
|Concave mirror||Concave lens|
|(i) It is opaque.||(i) It is transparent.|
|(ii) It causes reflection of light.||(ii) It causes refraction of light.|
|(iii) It forms real, inverted, erect and magnified||(iii) It forms only virtual, erect and diminished|
|Convex mirror||Concave mirror|
|(i) The reflecting surface of the convex mirror is bulged outwards.||(i) The reflecting surface of the concave mirror is curved inwards.|
|(ii) Convex mirror produce virtual, image.||(ii) Concave mirror forms either real or virtual image.|
|(iii) Convex mirror always produce diminished image.||(iii) Concave mirror produce either diminished or magnified image.|
|(iv) It is also known as diverging mirror.||(iv) It is also known as converging mirror.|
What are the characteristics of images formed by a concave mirror?
Following are the characteristics of images formed by a concave mirror:
- The image is not always of the same size as the object.
- The image is formed on the screen and the type of images which are formed on screen are called real images.
- The image is inclined when the object is kept far away from the mirror. When it is brought very close to the concave mirror, an erect and enlarged image is formed.
What is meant by spectrum? Name the colours of spectrum in their order.
The band of seven colours dispersed by a glass prism is known as spectrum. The seven colours in a spectrum are violet, indigo, blue, green, yellow, orange, and red. It is also abbreviated as VIBGYOR.
Write a short note on Newton’s disc.
A Newton disc, invented by Isaac Newton, is a disc with seven segments in rainbow colours. When the disc is rotated fast, the colour get mixed together and the disc appears to be whitish. This is due to the phenomenon called persistence of vision. It was an important discovery as it proves that light is not white, but a mixture of colour. The seven colours used to paint Newton disc are violet, indigo, blue, green, yellow, orange and red. See Fig. 15.16.
Light Class 7 Extra Questions HOTS
Rajesh for observing dispersion of light, used light from laser torch to fall on a prism. Will he be able to observe a band of seven colours?
No, because laser torch gives out light of only one colour.
If the side mirror of a scooter is replaced by a plane mirror, will it cause any inconvenience to the driver?
Yes, it will cause inconvenience to the driver and he will not be able to see the traffic behind him properly.
The concave reflecting surface of a torch got rusted. What effect would this have on the beam of light from the torch?
The beam of light will be of lower intensity due to diffused or irregular reflection.
How can you obtain a real image of a distant object?
By using concave mirror or convex lens and a screen we can obtain a real image of a distant object.
How will you identify the three mirrors, i.e., convex, concave and plane mirror without touching them?
We can identify the mirrors by seeing the image formed by them.
- Images formed by plane mirror is always virtual, erect and of same size as that of object.
- Images formed by convex mirror is erect, virtual and smaller in size than the object.
- Image formed by concave mirror is real, inverted, virtual, erect, magnified and diminished depending upon the distance of object with respect to the mirror.
Light Class 7 Extra Questions Value Based (VBQs)
Vinita thought to make a solar cooker and she shared her idea with Ankita. Ankita felt very excited that Vinita is using one of the renewable source of energy. Ankita suggested Vinita to use concave mirror instead of plane mirror as reflector to get the maximum heat. Vinita liked the idea of Ankita and thanked her for valuable suggestion.
(a) What is a solar cooker? What is its use?
(b) Why concave mirror is better than plane mirror for getting maximum heat?
(c) Can you name other such devices which are sources of energy and are eco-friendly.
(d) What values of Ankita and Vinita are shown here?
(a) A solar cooker is a device which uses the energy of direct sunlight to heat, cook or pasteurize food or drink.
(b) Concave mirror converges the sunlight to a single point. Thus, generates more heat and cook the food faster.
(c) Solar water heater, wind mills, solar cells, etc.
(d) Ankita and Vinita, both, are eco-friendly, suggestive, friendly and caring to each other.