These AP 7th Class Science Important Questions and 11th Lesson Light Class 7 Extra Questions will help students prepare well for the exams.
Class 7 Science Light Extra Questions
Light Class 7 Important Questions
Question 1.
The image formed by a lens is always virtual, erect and smaller in size for an object kept at different positions in front of it. Identify nature of lens.
Answer:
The lens which always forms virtual, erect and smaller image in spite of the different positions of an object is called concave lens.
Question 2.
Define ‘Reflection’.
Answer:
Reflection is the bouncing back of a ray of light after striking a reflecting surface.
Question 3.
How does light travel from one point to the other?
Answer:
Light travel from one point to the other in straight line.
Question 4.
Define real image.
Answer:
The image which can be obtained on a screen is called a real image.
Question 5.
What is VIBGYOR?
Answer:
It represent the order of seven colours in the rainbow i.e., violet, Indigo, blue, green, yellow, orange and red.
Question 6.
What is virtual image?
Answer:
The image formed by a plane mirror cannot be captured on a screen, and is called a virtual image.
Question 7.
What is image of an object?
Answer:
Due to the reflection of light, the impression of an object formed in a mirror is called the image of the object.
Question 8.
What is the dispersion of light?
Answer:
The splitting of white light into seven colours is called dispersion of light.
Question 9.
What happens when light falls on abolished or a shiny surface?
Answer:
When light falls on a polished shiny surface, it gets reflected.
Question 10.
How can we change the path of light?
Answer:
We can change the path of light by keeping any shiny or polished or reflecting material in the path of the light beam.
Question 11.
What is concave mirror?
Answer:
The mirror whose reflecting surface is concave (and polished surface is convex) is called a concave mirror. It is also known as a converging mirror.
Question 12.
How can we change the direction of the light?
Answer:
We can change the direction of light by the phenomenon called reflection.
Question 13.
What is a lens?
Answer:
A lens is a piece of transparent medium bounded by two surfaces in which at least one has curved surface.
Question 14.
What is prism?
Answer:
Prism is a transparent glass pyramid bounded by four triangular surfaces that separates white colour into a spectrum of colours.
Question 15.
Is the image formed by a plane mirror is always upright?
Answer:
Yes, the image formed by the plane mirror is always upright.
Light Extra Questions
Question 1.
The concave reflecting surface of a torch got rusted. What effect would this have on the beam of light from the torch?
Answer:
If the concave reflecting surface of a torch got rusted, it will produce diffused beam of light with lower intensity.The objects will not be clearly visible in this diffused and lower intensity of light.
Question 2.
What type of mirror is used by the dentist and other doctors? Why?
Answer:
A concave mirror is used by doctors for examining eyes, ears, nose, and throat as it gives an enlarged view of the targeted object.
Question 3.
What do you mean by lateral inversion? Give a suitable example.
Answer:
When an object is placed in front of a plane mirror, then the right side of the object appears to be the left side of the image and the left side of the object appears to be the. right side of the object. This side of changes of an object and its mirror image is called lateral inversion. For example, the word ‘AMBULANCE’ on an ambulance is written in micro writing.
Question 4.
How is the rainbow formed?
Answer:
A rainbow is formed by the refraction and reflection of the sun’s rays through raindrops. When it is raining in one part of the sky and sunny in another, a rainbow appears. The centre of the rainbows arc is always directed away from the sun.
Question 5.
Draw concave and convex lens.
Answer:
Question 6.
The distance between an object and a convex lens is changing. It is noticed that the size of the image formed on a screen is decreasing. Is the object moving in a direction towards the lens or away from it?
Answer:
In case of convex lens, when we move the object away from the lens, the size of image decreases and ultimately, when object is at infinite distance a point image is formed at the focus of lens.
Question 7.
What are the spherical mirrors? Give their types.
Answer:
Mirrors having curved surfaces are known as spherical mirrors. Their name is so, because they are considered as a part of a hollow sphere.Mirrors are mainly of two types: concave mirrors and convex mirrors.
Concave mirrors: Its reflecting surface is curved inwards.
Convex mirrors: Its reflecting surface is bulged out.
Question 8.
State any two uses of convex lens.
Answer:
Two uses of convex lens are :
- Convex lens is used as magnifying glass.
- Convex lens is used in spectacles, camera, microscope, telescope and binoculars.
- Convex lens are used in telescope.
Question 9.
What happens when the light falls on the mirror?
Answer:
The mirror changes the direction of light that falls on it when light falls on the mirror it reflects back in a different direction.
Question 10.
What type of mirror is used as a side mirror in a scooter? Why is this type of mirror chosen?
Answer:
A convex mirror is used as a side mirror in scooters. This type of mirror is chosen as it forms a smaller and virtual image. So, it can be used to see a much larger area than the area visible by a plane mirror.
Question 11.
Why do we need a shiny surface for reflection?
Answer:
The extent of reflection depends upon the shine and smoothness of the surface. So, greater the shining and smoothness of the surface, greater will be the reflection. So, this is a reason why we require a shiny surface for reflection.
Question 12.
What did Newton demonstrate by his experiments with the prism?
Answer:
Newton demonstrated by his experiments with the prisms that white light consists of a mixture of seven colours.
Question 13.
Why a convex lens and a concave lens are called coverging lens and diverging lens respectively?
Answer:
A convex lens converger the light generally falling on it. Therefore it is called converging lens. On the other hand, a concave lens diverges the light and is called diverging lens.
Extra Questions of Light Class 7
Question 1.
You are given three mirrors of different types. How will you identify each one of them?
Answer:
We can identify the mirrors by forming images of an object which are given as below:
- Plane mirrors: In case of a plane mirror the image formed will be virtual, erect and of the same size as that of the object.
- Concave mirrors: In the case of a concave mirror the image formed may be virtual or real, erect or inverted, magnified or diminished depending upon the position of the object.
- Convex mirror : In the case of a convex mirror the image formed will always be virtual, erect, and diminished.
Question 2.
Explain Newton’s experiment by which he proved that white light is made up of light of seven colours.
Answer:
Newton’s experiment: The idea that sunlight consists of several colours was first put forward by Sir Isaac Newton. He passed a narrow beam of light into a prism. The light that emerged from the prism was found to be coloured as in a rainbow. He gave the name spectrum to this coloured A prism splits a beam of sunlight into seven colours patch of light.
The spectrum was seen to consist of seven colours of light – violet, indigo, blue, green, yellow, orange and red. The various colours found in white light can be easily remembered as VIBGYOR. The process of splitting up of white light into different colours is called dispersion of light.
Question 3.
What is a lens ? Describe the two types of lens and their role in our day to day life.
Answer:
A lens is a piece of any transparent glass bound by the two curved surfaces or by one curved and one plane surface.When light rays pass through a lens, they bend and change their direction.
There are two types of lens. They are : concave lens and convex lens.
Convex lenses: Convex lens is thick in the middle and thin at its edge. When light rays pass through a convex lens, they bend inwards and converge at a common point to form an image of the source of light. Rays from the sun converge to form its image as a bright spot. A convex lens converges light rays. Therefore, it is also called a converging lens.
The image formed when the object is placed close to a convex lens is virtual, , erect and magnified. Virtual images cannot be caught on a screen. Images that are caught on a screen are called real images. When the object is placed at a distance from a convex lens, the image formed is real, inverted and diminished.
Concave lens : Concave lens is thin at the centre and thicker at edge. It is a lens that possesses at least one surface that curves inwards. When light rays are incident on a concave lens, they bend outwards or diverge. The rays diverge away from each other. Thus, a concave lens is also called a diverging lens.
A concave lens is thinner at its centre than at its edges, and is used to correct short sightedness. It does not focus at a single point. The image formed by a concave lens is upright, virtual and smaller than the object. For example, the images seen through a peephole are different from normal holes, because these peep holes contain concave lenses.
Question 4.
What is the Newtons disc ? Why does it appear white when rotated ?
Answer:
A circular disc constructed by Newton which is divided into seven parts painted with seven colours is known as Newtons disc. The colours painted on disc are those of spectrum of visible light. When the disc is rotated fast, the colours get mixed together and the disc appears to be whitish.This appearance of white light on rotating disc suggests that white light consist of seven colours.
Question 5.
Differentiate between concave mirror and convex mirror.
Answer:
Differences between concave mirror and convex mirror are as follows :
| S.No. | Concave mirror | Convex mirror |
| 1) | Spherical mirrors whose inner side is reflecting are called concave mirrors. | Spherical mirrors whose outer side is reflecting are called convex mirrors. |
| 2) | It can form real and virtual image. | It always form virtual image. |
| 3) | It is also called converging mirror. | It is also called diverging mirror. |
| 4) | It can form a magnified image. | It can form a diminished image. |
| 5) | It can form both erect and inverted image. | It always forms an image. |
Question 6.
Differentiate between real and virtual images.
Answer:
Difference between real and virtual images are as follows :
| S.No. | Virtual image | Real image |
| 1. | The image that can not be obtained on a screen is called a virtual image. | The image that can be obtained on a screen is called a real image. |
| 2. | It is always erect. | It is always inverted. |
| 3. | It is formed always behind the mirror. | It is obtained on the same side of mirror as the object. |
| 4. | It’s formed by a plane mirror and concave lens. | It’s formed by a concave mirror and convex lens. |
| 5. | Rays converge at a point to form the image. | Rays appear to diverge from a point where the image is formed. |
Question 7.
How will you come to know that the mirror given to you is a concave or convex?
Answer:
In the concave surface the polish is done on its outer surface and the inner surface is shining. If we bring it closer to our face the later will look very big. In a convex mirror the polish is done on the inner surface and then outer side is shining. In this mirror our face will always appear to be shorter.
Question 8.
Write any two uses of concave mirror and convex mirror.
Answer:
Uses of concave mirror:
- They are used in reflected of car, head-lights and search lights.
- They are used as shaving mirrors.
- They are used by dentists to see an enlarged image of teeth.
- They are used in telescopes.
Uses of convex mirror:
- They are used in automobiles by the drivers for seeing the erect images of the,traffic.
- They are used as staircase mirrors on the double decker buses.
- They are used as rear view mirrors in automobiles such as buses, cars, scooters, trucks etc., to see the traffic coming from behind.
Case Based / Data – Based Questions
Priya’s sister, Shreya was preparing the dinner in her kitchen for Priya and her bother. Both of them were feeling so much hungry and they sat ideally on their respective chairs and having empty plates and spoons on their dinning table. They were shouting like a 5 years old child that they wanted the dinner so much eagerly in order to fulfil their stomach.
At the sometime, Priya’s sister observed the cooked food to both of them and the moment, when Priya was just about to eat the rice with the help of spoon, she noticed that the. spoon has such a shining surface that it reflected the light rays incident on it.
a) Explain the importance of shining surface in the reflection of light.
Answer: As we know that the extent of reflection depends upon the shining of surface. So, greater the shining of the surface, more will be the reflection.
b) Name the type of spherical mirror represented by the shining steel spoon.
Answer: Both convex and concave mirrors are represented by the shining steel spoon.
c) What do you mean by reflection?
Answer: Reflection is the bouncing back of a ray of light after striking a reflecting surface.
d) What type of mirror is represented by the backside of a shining steel spoon?
Answer: The backside of the steel spoon acts as a convex mirror (diverging mirror)