Podcast
Questions and Answers
What is the power of a lens that has a focal length of 20 cm?
What is the power of a lens that has a focal length of 20 cm?
- -2.5 D
- 2.5 D
- -5.0 D
- 5.0 D (correct)
A diverging lens has a power of -3.0 D. What is its focal length?
A diverging lens has a power of -3.0 D. What is its focal length?
- -0.33 m
- 0.67 m
- -0.67 m
- 0.33 m (correct)
In which situation does a convex lens form a virtual image?
In which situation does a convex lens form a virtual image?
- Object at the focal point
- Object between the lens and its focal point (correct)
- Object beyond twice the focal length
- Object at infinity
If a concave lens has a power of -4.0 D, what is its focal length?
If a concave lens has a power of -4.0 D, what is its focal length?
What type of image does a concave mirror produce with an object placed between the mirror and its focal point?
What type of image does a concave mirror produce with an object placed between the mirror and its focal point?
For a converging lens, if the object is placed at twice the focal length, where is the image formed?
For a converging lens, if the object is placed at twice the focal length, where is the image formed?
What is the relationship between the power and focal length of a lens?
What is the relationship between the power and focal length of a lens?
In what scenario does refraction not occur as light passes through different media?
In what scenario does refraction not occur as light passes through different media?
A ray of light enters a glass slab at an angle of incidence of 30 degrees.What will be the angle of refraction inside the glass slab?
A ray of light enters a glass slab at an angle of incidence of 30 degrees.What will be the angle of refraction inside the glass slab?
If an object is placed at twice the focal length from a convex lens, what type of image will be formed?
If an object is placed at twice the focal length from a convex lens, what type of image will be formed?
Study Notes
Sign Convention for Reflection by Spherical Mirrors
- The New Cartesian Sign Convention is used to deal with the reflection of light by spherical mirrors.
- The pole (P) of the mirror is taken as the origin.
- The principal axis of the mirror is taken as the x-axis (X'X) of the coordinate system.
- The object is always placed to the left of the mirror.
- Distances parallel to the principal axis are measured from the pole of the mirror.
- Distances measured to the right of the origin (along +x-axis) are taken as positive.
- Distances measured to the left of the origin (along –x-axis) are taken as negative.
- Distances measured perpendicular to and above the principal axis (along +y-axis) are taken as positive.
- Distances measured perpendicular to and below the principal axis (along –y-axis) are taken as negative.
Mirror Formula and Magnification
- The distance of the object from the pole of the mirror is called the object distance (u).
- The distance of the image from the pole of the mirror is called the image distance (v).
- A negative sign in the value of the magnification indicates that the image is real.
- A positive sign in the value of the magnification indicates that the image is virtual.
Image Formation by Spherical Mirrors
- Convex mirrors produce virtual, erect, and smaller images.
- Concave mirrors produce real, inverted, and larger or smaller images.
- The mirror formula is given by: 1/f = 1/do + 1/di
- Magnification, m = -di/do = height of image / height of object
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Description
Test your knowledge on the sign conventions followed while dealing with the reflection of light by spherical mirrors, including the New Cartesian Sign Convention and the placement of the object in relation to the mirror.
