Basic Science Solutions for Class 7 Science Chapter 8 Light are provided here with simple step-by-step explanations. These solutions for Light are extremely popular among class 7 students for Science Light Solutions come handy for quickly completing your homework and preparing for exams. All questions and answers from the Basic Science Book of class 7 Science Chapter 8 are provided here for you for free. You will also love the ad-free experience on Meritnation’s Basic Science Solutions. All Basic Science Solutions for class 7 Science are prepared by experts and are 100% accurate.

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Rectilinear propagation of light is the property of light due to which it travels in a straight line.

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The incident ray and the reflected ray make equal angles with the surface of the plane mirror.

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The image formed by a plane mirror is virtual and erect, and its size is the same as that of the object.

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When an object is placed beyond the focus of a concave mirror, the image formed is real and inverted.

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When an object is placed beyond the focus of a convex lens, the image formed is real and inverted.

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We will place an object closer to a concave mirror than the focus of the mirror to see an erect and magnified image.

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We place an object between a convex lens and its focus to obtain an erect and magnified image.

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The following are two uses of a concave mirror.
(a) It is used to converge sunlight.
(b) It is used as a compact mirror and as a shaving mirror.

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Two uses of a convex lens are:
(a) It is used in a magnifying glass.
(b) It is used in spectacles.

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White light is a mixture of seven colours and looks colourless.

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The image formed by a pinhole is inverted because, when the rays from an object cross the pinhole, the rays from the top half of the object are below the rays from the bottom half. So, when they fall on a screen, an inverted image is formed.

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A reflecting surface may have a concave reflecting surface or a convex reflecting surface.
When parallel rays fall on a concave reflecting surface, then, after reflection, the rays converge to a point.
When parallel rays fall on a convex reflecting surface, the rays seem to diverge from a point.

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Convex mirrors are used as rear-view mirrors because they form images that are much smaller than the objects. Therefore, we can view a wider area on a convex mirror.

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White light when gets split into its component colours, it gets split into seven colours called the spectrum of white light. The colours that constitute white light are violet, indigo, blue, green, yellow, orange and red (VIBGYOR).

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When sunlight passes through raindrops at certain angles, white light bends very sharply and the seven colours of white light are separated. These colours are visible in the sky as a rainbow.

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When Newton's disc is rotated, it appears white, because when the disc spins, all the colours pass through a spot rapidly one after another. This rapid movement has the effect of putting all the colours in one place, making them appear white.

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A real image is an image that can be formed on a screen.
A virtual image is an image that cannot be formed on a screen.

Real image Virtual image
Real images are formed when the rays actually meet after reflection or refraction. When a virtual image is formed, the rays do not meet after reflection or refraction but are extended to form the image.
A real image is always inverted when it is formed by one mirror or lens. A virtual image is always erect when it is formed by one mirror or lens.

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The point at which parallel rays of light falling on a curved surface actually meet or seem to meet (when extended) after reflection from the surface is called the focus of the curved surface.

To find the focus of a convex lens, take a convex lens or a magnifying glass. Turn the lens towards the sun and slowly move it away from the ground. At a certain distance from the ground, we see a sharp image of the sun at a point. This point, at which parallel rays of the sun converge after passing through the lens, is called the focus of the lens.

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Refraction of light refers to the bending of light when it travels from one medium to another.
Example: If we look carefully at raindrops on leaves and flowers in a garden, we will be able to see inverted images of the garden in them. We will also see magnified images such as those of veins of leaves. All these images are formed because of refraction of light.

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1. An image formed by a plane mirror cannot be seen on a screen.
2. A real image can be formed on a screen.
3. A convex mirror is one in which the reflecting surfaces bulges out.
4. After parallel rays of light pass through a concave lens, they seem to come from a point.
5. A magnifying glass is a convex lens.



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(c) Concave lens

A concave lens forms only virtual images.

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(a) refraction

A drop of water forms a magnified image of the veins because of refraction.

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(c) colourless light

If we mix all the colours of a rainbow, we get white light, which is colourless.

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(a) increase

If you bring a faraway object towards the focus of a convex lens, the size of the image increases.

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(b) Inverted images in a pinhole camera and (c) shadow

Inverted images are formed in a pinhole camera because of the rectilinear propagation of light. Rectilinear motion of light also leads to formation of shadows.

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Position of the object Image type Side on which image is formed
1. In front of a plane mirror A. Real m. On the side of the incident ray
B, C, G, n B. Virtual n. On the other side of the incident ray
2. In front of a convex mirror C. Erect  
B, C, E, n D. Inverted  
3. In front of a concave lens E. Always smaller  
B, C, E, m F. Always larger  
4. Beyond the focus of a concave mirror G. Same size  
A, D, m    
5. Beyond the focus of a convex lens    
A, D, n    
6. Closer than the focus of a convex lens    
B, C, F, m    



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