Solved NCERT Questions For Class 7 Science Chapter 15 In Hindi - Free PDF
FAQs on NCERT Solutions For Class 7 Science Chapter 15 Light in Hindi - 2025-26
1. What are the key characteristics of an image formed by a plane mirror as per the solutions for NCERT Class 7 Science, Chapter 15?
As per the CBSE guidelines for the 2025-26 session, the solutions for Chapter 15 explain that an image formed by a plane mirror has the following characteristics:
It is virtual (cannot be formed on a screen).
It is erect or upright.
It is of the same size as the object.
The image is formed at the same distance behind the mirror as the object is in front of it.
It is laterally inverted, meaning the left side of the object appears as the right side of the image.
2. How do you correctly answer questions from the NCERT exercises about the uses of concave and convex mirrors?
To solve these questions correctly, you must link the mirror's property to its use.
For a concave mirror: State that it forms a magnified, erect image when the object is close. This property is why it's used by dentists to see an enlarged view of teeth. It also converges light, making it useful in torches and headlights.
For a convex mirror: State that it provides a wider field of view and forms a diminished, erect image. This is why it is used as a rear-view mirror in vehicles, allowing drivers to see more of the traffic behind them.
3. Which type of mirror specified in Chapter 15 can form a real image, and under what condition?
The correct answer for the NCERT exercise is the concave mirror. A concave mirror can form a real image, which can be projected onto a screen. This only happens when the object is placed at a distance greater than the focal length of the mirror. When the object is placed closer than the focal length, a concave mirror forms a virtual image instead.
4. What is the correct step-by-step method to explain the dispersion of light through a prism as per the NCERT curriculum?
To correctly explain the concept for the NCERT solutions, follow these steps:
Step 1: State that sunlight, which appears white, is actually a mixture of seven colours.
Step 2: Explain that when a beam of white light is passed through a glass prism, it splits into its constituent colours.
Step 3: List the band of seven colours, known as a spectrum, in the correct order: Violet, Indigo, Blue, Green, Yellow, Orange, and Red (VIBGYOR).
Step 4: Conclude that this phenomenon of splitting white light into its component colours is called dispersion of light.
5. Why is a convex lens able to form a real image while a concave lens cannot?
This is a key conceptual difference needed for solving NCERT problems. A convex lens is thicker in the middle and is a converging lens. It bends the parallel rays of light passing through it inwards to meet at a single point (the focus). This convergence allows it to form a real image that can be captured on a screen. In contrast, a concave lens is thinner in the middle and is a diverging lens. It spreads the light rays outwards, so they never actually meet. They only appear to come from a point, thus forming a virtual image that cannot be projected.
6. How does the fundamental principle 'light travels in a straight line' become the basis for solving ray diagram problems in Chapter 15?
The principle that light travels in a straight line, called rectilinear propagation of light, is the foundation for constructing any ray diagram. To solve a problem, we assume that rays of light originating from an object travel in straight lines until they strike a mirror or a lens. The path of these rays changes only upon reflection or refraction. By accurately drawing at least two of these straight-line rays and their paths after interacting with the optical device, we can determine the precise location and nature of the image where the rays intersect (or appear to intersect).
7. When solving NCERT questions, why is it a common mistake to misidentify an image from a concave mirror as always real?
A common mistake is to memorise that concave mirrors form real images without understanding the underlying condition. The NCERT solutions require a precise understanding of the object's position. A concave mirror forms a real and inverted image only when the object is placed beyond its focal point. However, if the object is placed between the pole and the focal point of the mirror, it forms a virtual and magnified image. Forgetting this exception is a frequent error in solving problems related to image formation by concave mirrors.
8. What is the key difference in the method to locate an image in a plane mirror versus a convex mirror for NCERT exercises?
The method differs based on the mirror's properties.
For a plane mirror, the method is direct: the image is always virtual, erect, and located at the same distance behind the mirror as the object is in front of it. The size is always the same as the object.
For a convex mirror, the method involves understanding that it always forms a virtual, erect, and diminished image, regardless of the object's position. The image is always located between the pole and the focus. Therefore, while both can form virtual images, the solving method for a convex mirror requires knowing that the image will always be smaller and closer to the mirror than the object.






















