Class 7 Science Chapter 13 Question Answers - Light

Very Short Q & A :

Q1: Give an example to show that the path of light is always straight and never curved.

Ans: Light emitted by torchlight and light emitted from the headlights of a vehicle

Q2: The bouncing of light by any smooth surface, like a mirror, is called__________________.

Ans: Reflection of light.

Q3: What is the image of an object?

Ans: Due to the reflection of light, the impression of an object formed in a mirror is called the image of the object.

Q4: As the distance of the object from the mirror increases, the distance of the image also increases. True/ False.

Ans: True

Q5: Placing a mirror near lights, and table lamps reflect the light over a larger area and make the room appear brighter. True/ False.

Ans: True.

Q6: Images that cannot be captured on a screen are called __________________.

Ans: Virtual images.

Q7: Ravi is looking in a mirror; his right hand will appear to be at ____________ in its image in the mirror.

Ans: Left side

Q8: Why the word ‘AMBULANCE’ is painted left-right inversed on the vehicle?

Ans: So that when the driver of a vehicle in front looks into his rear - view mirror, can read ambulance written on it quickly and give way to it.

Q9: The image formed by a plane mirror is

1. The same size as that of the object
2. Left-right inversed
3. Erect and virtual
4. All of the above

Ans: (4) All of the above.

Q10: State the principle used in creating a mirror image.

Ans: Principle of reflection

Q11: Name the mirror having a curved reflecting surface.

Ans: Spherical mirror

Q12: Name the two types of spherical mirror.

Ans: Concave mirror and convex mirror.

Q13: State uses of the concave mirror.

Ans: Concave mirrors are used by dentists to obtain a magnified image of the teeth. They are also used in solar heaters or solar concentrators, and as reflectors in flashlights, and headlights of cars and scooters.

Q14: State uses of the convex mirror.

Ans: Convex mirror are used as reflectors at sharp turns and tricky or ‘blind’ corners and in parking lots, and as rear-view mirrors in cars and on motorcycles.

Q15: What is a virtual image?

Ans: The image formed by a plane mirror cannot be captured on a screen, and is called a virtual image.

Q16: What is a real image?

Ans: Images that can be captured on a screen are known as real images.

Q17: Give an example of a real image.

Ans: In a camera, images are real and can be captured on the negative, which acts as a screen.

Q18: In an opaque spherical surface, the silvered surface acts as a mirror. True/ False.

Ans: True

Q19: What happens when light rays are incident on a concave lens?

Ans: When light rays are incident on a concave lens, they bend outwards or diverge.

Q20: What is the name for the concave lens?

Ans: Diverging lens

Q21: What kind of image is formed by the concave lens?

Ans: Upright, virtual and smaller than the object.

Q22: Name an object made from the concave lens.

Ans : Peep holes contain concave lenses.

Q23: A convex lens converges light rays. Therefore, it is also called a ___________________.

Ans: Converging lens

Q24: What kind of image is formed by the convex lens?

Ans: Virtual, erect and magnified.

Q25: State various applications of lenses.

Ans: Lenses are used in magnifying glasses, peepholes, cameras, bioscopes, binoculars, telescopes, microscopes, and projectors.

Q26: A refracting telescope uses a:

1. Concave mirror
2. convex lens
3. Convex mirror
4. Both a and c

Ans: (4) Both 1 and 2.

Q27: How is rainbow formed in the sky?

Ans: A rainbow is formed by the refraction and reflection of the sun’s rays through raindrops.

Q28: When does rainbow appear in the sky?

Ans: When it is raining in one part of the sky and sunny in another, a rainbow appears.

Q29: Although sunlight appears white, it is composed of _________________colours.

Ans: Seven

Q30: The colors in a rainbow are not the colors of sunlight. True/ False.

Ans: False.

Q31: An image formed by a______________mirror is always of the same size as that of the object.

Ans: Plane

Q32: A concave mirror always forms a real image. True/ False.

Ans: False

Q33: Which type of lens forms always a virtual image?

Ans: A concave lens always forms a virtual, erect and smaller image than the object.

Q34: What is the focal length of a plane mirror?

Ans: Infinite

Q35: State the relation between the radius of curvature and focal length of spherical mirrors.

Ans : 

Radius of curvature = 2 * focal length.

R = 2f.

Q36: Out of convex mirror and the concave mirror, whose focus is situated behind the mirror?

Ans: The focus of convex mirror is situated behind it.