CONTENT • Spherical mirror • Terms used in spherical mirrors • Image formed in concave mirror • Image formed in convex mirror • Mirror formula
• Applications
SPHERICAL MIRRORS
MIRRORS Mirrors are the surfaces that reflect almost all types of incident light rays that hit their surface. The mirror can have either a plane or a curved surface. On this basis, mirrors are divided into two: Spherical Mirrors and Plane Mirrors. The plane mirrors simply mirror having plain and polished reflecting surfaces while Spherical mirrors have curved reflecting surfaces.
SPHERICAL MIRRORS A spherical mirror is a mirror that has the shape of a piece cut out of a spherical surface. There are two types of spherical mirrors: ⚫ ⚫
concave mirror convex mirror.
Important Terms used in Spherical Mirrors Pole: The midpoint or the center point of the spherical mirror. It is represented by capital P. All the measurements are made from it only. Aperture: An aperture of a mirror is a point from which the reflection of light actually takes place or happens. It also gives an idea about the size of the mirror. Principal axis: An imaginary line that passes through the optical center and from the center of curvature of a spherical mirror. All the measurements are based on this line.
Centre of Curvature: The point in the center of the mirror surface that passes through the curve of the mirror and has the same tangent and curvature at that point. It is represented by the capital letter C.
Radius of Curvature: It is considered as the linear distance between the pole and the center of curvature. It is represented by the capital letter R,
Principal Focus: Principal Focus can be called the Focal Point also. It is present on the axis of a mirror where the rays of light parallel to the principal axis converge or appear to converge or diverge after reflection.
Focus: It is any given point on the principal axis where light rays parallel to the principal axis will converge or appear to converge after getting reflected from the mirror.
Image Formation by Concave Mirror and their ray diagrams When the object is placed at infinity ⚫
The image will form at F
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Point-sized image
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highly diminished in size
Real inverted image.
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When the object is placed between infinity and the Centre of Curvature ⚫
The image is formed between the center of curvature (C) and focus (F)
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Diminished
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Real
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Inverted
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Object at Centre of Curvature (C) ⚫
image formed at c
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Real
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Inverted
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Same size as the object
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The object is between the Centre of curvature (C) and Principal Focus (F) ⚫
Image is formed beyond the center of curvature (C)
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Real
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Inverted
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Magnified
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Object at Principal Focus (F)
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Image of the object is formed at infinity Highly enlarged image
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Real
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Inverted
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The object between Principal Focus (F) and Pole (P) ⚫
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Image formed behind the mirror Enlarged
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Virtual
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Erect
Image Formation by Convex Mirror and their ray diagrams ⚫
Object at infinity ⚫
Image is formed at the principal focus behind the convex mirror
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Highly diminished
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Virtual
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Erect
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Object is between infinity and the pole ⚫
Image formed between the pole and focus behind the mirror
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Diminished
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Virtual
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Erect
MIRROR FORMULA To do the sums related to the spherical mirrors, the formula used is known as the mirror formula. It is used to calculate the focal length, image distance, object distance, and also magnification or any other thing required. u = object distance v = image distance
f = focal length of mirror
Sign Conventions for Spherical Mirrors
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Usually, if the object is located on the left side of the principal axis from the mirror then the object distance is taken negatively. While if it is located on the right side it is taken to be positive. The sign of focal length depends on the type of mirror we are using, as for the concave mirror it is negative and for the convex mirror on the other hand is positive always. It is to be mentioned again that we have to follow the sign conventions strictly to get the correct
Applications of Concave Mirrors ⚫
Used in shaving mirrors
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The concave mirror used in the ophthalmoscope
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Uses of the concave mirrors in astronomical telescopes
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Concave mirrors used in the headlights of vehicles
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Used in solar furnaces
Application of Convex Mirror ⚫
Convex mirrors used inside buildings
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The convex mirrors used in vehicles
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Uses of the convex mirror in a magnifying glass
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Convex mirrors used for security purposes
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Convex mirrors are also used in various other places like street light reflectors as they can spread light over bigger areas.