Image Formation by Spherical Mirror-You might have observed that the image formed in the side view mirror of a car is smaller while the image formed in the rear-view mirror is larger than the actual size of the objects. The dentist uses a small mirror to examine the teeth of a patient.
You might have also observed that for shaving purposes different mirrors are used. So, the different spherical mirrors are used for different purposes.
We will discuss the spherical mirror in this article.
Table of Content
What are Spherical Mirrors?
Spherical mirror is a type of mirror whose reflecting surface is the part of a hollow sphere of glass. There are two types of spherical mirrors: concave mirrors and convex mirrors.
Concave mirrors
The inward curve of these mirrors resembles the interior of a sphere. On the inside of the curve, they have a reflective surface. Concave mirrors are helpful for focusing light on devices like cosmetics mirrors, telescopes, and headlights because they can converge light rays to a focal point.
Convex mirrors
Convex mirrors protrude outward, resembling a sphere’s outside. On the outside of the curve, they have a reflective surface. Convex mirrors distort light waves, giving the impression that objects are wider and smaller than they actually are. They are frequently utilized in applications like security mirrors in retail establishments and rear-view mirrors in automobiles.
Check: Concave and Convex Mirrors
Rules for Image Formation by Spherical Mirrors
Rule 1
- For concave mirror: A ray of light parallel to the principal axis will pass through the focus after reflection.
- For Convex mirror: A ray of light parallel to the principal axis will appear to come from focus.
Rule 1
Rule 2
- For concave mirror: A ray passing through the principal focus(F) becomes parallel to the principal axis.
- For convex mirror: A ray directed towards principal focus becomes parallel to the principal axis.
Rule 2
Rule 3
- For Concave mirror: A ray passing through the centre of curvature will take the same path after reflection.
- For convex mirror: A ray directed towards the centre of curvature will take the same path after reflection.
Rule 3
Rule 4
- For any ray incident at any angle at the pole(P), the reflected ray follows the law of reflection for both concave as well as convex mirrors.
Rule 4
Image Formation by Concave Mirror
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When an object is placed beyond C (centre of curvature): When an object AO is placed in front of a concave mirror, the object is placed beyond the centre of curvature of the concave mirror. The image formed after the reflection will be between the centre of curvature (C) and focus(F). The size of the image will be smaller than the object. The nature of the image will be real and inverted.
- Image formed at – Between C & F
- Image nature – Real & inverted.
- Image size – Smaller than the object
When an object is placed beyond C, then an image is formed between C & F.
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When an object is placed at C: When an object AO is placed in front of a concave mirror, at the centre of curvature of the concave mirror. The image formed after the reflection will be at the centre of curvature (C). The size of the image will be equal to the object. The nature of the image will be real and inverted.
- Image formed at – At C
- Image nature – Real & inverted
- Image size – Same size as the object
When an object is placed at C, an image is also formed at C only.
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When an object is placed between F & C: When an object AO is placed in front of a concave mirror, between the centre of curvature and the focus of the concave mirror. The image formed after the reflection will beyond the centre of curvature (C). The size of the image will be larger than the object. The nature of the image will be real and inverted.
- Image formed at – Beyond C
- Image nature – Real & inverted
- Image size – Larger than the object
When an object is placed between F & C, the image is formed beyond C.
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When an object is placed between F and P: When an object AO is placed in front of a concave mirror, between the focus (F) and the pole(P) of the concave mirror. The image formed after the reflection will be behind the mirror. The size of the image will be larger than the object. The nature of the image will be virtual and erect.
- Image formed at – Behind the mirror
- Image nature – Virtual and erect
- Image size – Larger than the object
Image Formation by Convex Mirror
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When an object is placed anywhere between ∞ and Pole: When an object AB is placed in front of a convex mirror at any point between Infinity (∞) and the pole (P). The image will always be formed behind the mirror. The nature of the image will be virtual and erect. The size of the image will be smaller than the object.
- Image formed at – Behind the mirror
- Image nature – Virtual & Erect
- Image size – Smaller than the object
When an object is placed anywhere between ∞ and Pole, the image will form behind the mirror.
Check: Mirror Formula and Magnification
Sample Questions
Question 1: Riya stands in front of a spherical mirror. She finds that her image has a very fat body. Tell us what was the shape of the mirror?
Answer:
As the image has very fat body means she is standing in front of a concave mirror.
Question 2: Raj was standing in front of the mirror, he raised his right hand but in the mirror, he saw his left hand. The image is the same size as the size of his body. Tell us, what was the type of mirror in front of him.
Answer:
As the size of the image is equal to size of his body and he saw his left hand right and vice versa. So, he was standing in front of a plane mirror.
Question 3: Two concave mirrors have the same focal length but the aperture of one is larger than that of the other. Which mirror forms the sharper image and why?
Answer:
As the concave mirror with smaller aperture is free from spherical aberration. So, concave mirror with smaller aperture forms sharper image.
Question 4: Can we increase the range of a telescope by increasing the diameter of its objective?
Answer:
Yes, because the light gathering power of objective will increase and even faint objects will be visible.
Question 5: A convex mirror is kept underwater. What would be the change in the focal length of the mirror?
Answer:
As the focal length of a spherical is independent of nature of the medium. So, the focal length of the convex mirror doesn’t change.
Related Articles:
Image formation by Spherical Mirror- FAQs
What is a spherical mirror?
Spherical mirrors are mirrors that have a curved, spherical surface
What is mirror image formation?
This occurs when object is positioned in front of a mirror and the same object is seen in the mirror.
What is the image formed by a spherical surface?
The type of spherical surface and the object’s position in relation to it define the image that is created by it, such as a spherical mirror or lens
What are the 3 types of mirrors?
The three types of mirrors are:
- Concave Mirror
- Convex Mirror
- Plane Mirror
What is mirror formula?
The mirror formula is the relationship between the focal length of the mirror, the object’s distance, and the image’s distance. It is given by. 1 u + 1 v = 1 f.
Can we see our image in spherical mirror?
Yes, we can see our image in a spherical mirror.
What are the two types of spherical image?
The two types of spherical images formed by spherical mirrors are:
- Real Image: A real image is formed when light rays actually converge at a point.
- Virtual Image: A virtual image is formed when light rays appear to diverge from a point behind the mirror.
What are the 4 rules of concave mirror?
- Any incident ray traveling parallel to the principal axis will pass through the focal point after reflection.
- Any incident ray passing through the focal point will travel parallel to the principal axis after reflection.
- Any incident ray passing through the center of curvature will reflect back on itself, retracing its path.
- The image formed by a concave mirror can be real or virtual, depending on the position of the object relative to the mirror.