Light Class 7 Worksheet Science Chapter 13

Q.1. True/False
(i) We can obtain an enlarged and erect image by a convex mirror.

False

A convex mirror:

• Always produces a virtual image.
• The image is smaller than the object.
• It cannot create an enlarged image.

(ii) A concave lens always form a virtual image.

True

• A concave lens always produces a virtual image.
• This image is:
  • Upright (erect)
  • Smaller than the object

(iii) We can obtain a real, enlarged and inverted image by a concave mirror.

True

A concave mirror can indeed produce a:

• Real image
• Enlarged image
• Inverted image

This occurs when the object is placed at a distance greater than the focal lengthof the mirror.

(iv) A real image cannot be obtained on a screen.

False

A real image can be projected onto a screen because it is created by the actual convergence of light rays. This means:

• It forms where light rays meet.
• It can be displayed on a surface, like a screen.

(v) A concave mirror always form a real image.

False

A concave mirror can create:

• Real images when the object is placed far from the mirror.
• Virtual images when the object is close to the mirror.

Thus, the statement is false.

(vi) In the mirror the right appears left and the left appears right.

True
The effect observed in a mirror is called lateral inversion. This means:

• The right side of an object appears on the left side of its mirror image.
• Conversely, the left side appears on the right side.
• Only the sides are reversed; the image does not appear upside down.

Q.2. Fill in the blanks.
(i) An image that cannot be obtained on a screen is called ____.

virtual image
A virtual image is one that cannot be projected onto a screen because the light rays do not actually converge at the location of the image.

(ii) Image formed by a convex ____ is always virtual and smaller in size.

mirror
The image formed by a convex mirror is always:

• Virtual - it cannot be projected onto a screen.
• Erect - the image appears upright.
• Smaller - it is reduced in size compared to the object.

(iii) An image formed by a ____ mirror is always of the same size as that of the object.

plane

• The image formed by a plane mirror is always erect.
• It is virtual and appears at the same distance behind the mirror as the object is in front of it.
• The size of the image is identical to that of the object.

(iv) An image which can be obtained on a screen is called a ____ image.

real
A real image is formed when light rays converge and can be projected onto a screen.

(v) An image formed by a concave ____ cannot be obtained on a screen.

lens

• An image formed by a concave lens is always virtual.
• This type of image cannot be projected onto a screen.
• It appears erect and smaller than the object.

(vi) A virtual image larger than the object can be produced by a _____.

concave mirror

• A concave mirror can produce a virtual image that is larger than the object.
• This occurs when the object is placed between the mirror's focus and its surface.
• The resulting image is erect and magnified.

Q.3. Give an example of a curved mirror.

The most common example of a curved mirror is a spherical mirror.

Q.4. What is real image?

An image which can be obtained on a screen is called a real image.

Q.5. What is convex mirror?

A convex mirror is a type of mirror with a curved surface that bulges outward. Key characteristics include:

• It produces a virtual image that is smaller than the object.
• The image appears erect (upright) and cannot be projected onto a screen.
• Commonly used in automobile side mirrors to provide a wider field of view.

Q.6. What makes things visible to us?

Objects are visible only when light reflected from them reaches our eyes.

Q.7. What kind of image is formed by concave lens?

A concave lens always forms:

• Erect images
• Virtual images
• Images that are smaller than the object

Q.8. What are the two types of spherical mirror?

The two types of spherical mirrors are:

• Concave mirrors: These have a reflective surface that curves inward, resembling the inside of a bowl.
• Convex mirrors: These have a reflective surface that bulges outward, similar to the outside of a ball.

Q.9. Write some uses of lenses.

Lenses are versatile optical devices with various applications:

• Spectacles: Correct vision by focusing light onto the retina.
• Telescopes 
• Microscopes: Magnify tiny objects for detailed examination.
• 
  
  • Camera lenses: Capture images by focusing light onto a sensor or film.
• Magnifying glasses: Aid in reading small print or observing fine details.

Q.10. What happens when light falls on a polished or a shiny surface?

When light strikes a polished or shiny surface, it is primarily reflected. This reflection occurs due to the smoothness of the surface, which allows light to bounce back in a consistent direction.

• The light does not scatter but reflects at the same angle it hits the surface.
• Common examples of such surfaces include mirrors, stainless steel, and calm water.
• This property is what makes these surfaces appear shiny and allows us to see reflections.

Q.11. What is diverging lens?

A diverging lens, also known as a concave lens, has the following characteristics:

• It diverges light rays that pass through it, causing them to spread out.
• It is thinner at the centre and thicker at the edges.
• The images formed by a concave lens are always virtual, erect, and smaller than the object.

Q.12. What is reflection of light?

The reflection of light occurs when a light ray bounces back after hitting a surface. 
Key points include:

• Light travels in straight lines.
• When light strikes a smooth surface, it changes direction.
• This change in direction is known as reflection.
• Common reflective surfaces include mirrors and calm water.

Q.13. Why we are not able to see the candle flame through a bent pipe?

We cannot see the candle flame through a bent pipe due to the way light travels. Here are the key points:

• Light travels in straight lines.
• A bent pipe alters the path of light, preventing it from reaching our eyes.

Thus, the flame is not visible when viewed through the bent pipe.

Q.14. What type of image does the outer side of a spoon show?

The outer surface of a spoon functions like a convex mirror. The image it produces has the following characteristics:

• Erect: The image appears upright.
• Virtual: The image cannot be projected onto a screen.
• Smaller: The image is reduced in size compared to the object.

Q.15. What is the nature of the image formed by a convex mirror?

The image formed by a convex mirror has the following characteristics:

• Erect: The image appears upright.
• Virtual: The image cannot be projected onto a screen.
• Smaller: The image is reduced in size compared to the object.

Q.16. What is concave mirror?

A concave mirror has a reflecting surface that curves inward. Here are some key points:

• The inner surface is the concave part.
• It can form both real and virtual images.
• Commonly used in applications like dentistry and torch reflectors.

Q.17. How can we change the path of light?

We can change the path of light by using any shiny or polished surface. Here are some examples:

• A stainless steel plate can redirect light.
• A steel spoon acts like a mirror.
• The surface of water can also reflect light.

In essence, any shiny surface can alter the direction of light. 

Q.18. What happens when light falls on a mirror?

A mirror changes the direction of light that hits it. This process is known as the reflection of light.

• When light strikes a mirror, it bounces back.
• This change in direction allows us to see our reflection.
• Mirrors can be made from various shiny surfaces, including polished metals and glass.

Q.19. When does rainbow appear in the sky?

A rainbow typically appears after rain when the sun is low in the sky. It manifests as a large arc in the sky displaying various colours.

Q.20. Why are concave and convex mirrors called spherical mirrors?

Concave and convex mirrors are referred to as spherical mirrors because:

• Their reflecting surfaces are segments of a hollow sphere.
• A concave mirror has a curved inward surface.
• A convex mirror has a curved outward surface.

These shapes allow them to focus or disperse light effectively.