subject

Lenses

Physics ⇒ Light and Optics

Lenses starts at 8 and continues till grade 12. QuestionsToday has an evolving set of questions to continuously challenge students so that their knowledge grows in Lenses. How you perform is determined by your score and the time you take. When you play a quiz, your answers are evaluated in concept instead of actual words and definitions used.
See sample questions for grade 9
A convex lens has a focal length of 10 cm. An object is placed 30 cm from the lens. Calculate the image distance.
A lens forms an image that is three times the size of the object and is real. What is the magnification?
A lens forms an image that is virtual, erect, and smaller than the object. What type of lens is it?
A lens has a power of -2 D. What type of lens is it?
A student places an object 5 cm from a convex lens of focal length 10 cm. What type of image is formed?
Describe the difference between a real and a virtual image.
If a convex lens has a focal length of 25 cm, what is its power?
If an object is placed at 2F in front of a convex lens, where will the image be formed?
If the focal length of a lens is 20 cm, what is its power in diopters?
If the object distance (u) is -15 cm and the image distance (v) is 30 cm, what is the focal length of the lens?
If the power of a lens is +4 D, what is its focal length in centimeters?
State one use of a concave lens in daily life.
State the lens formula relating object distance (u), image distance (v), and focal length (f).
What happens to the focal length of a lens if it is placed in a medium with a refractive index equal to that of the lens material?
What is the effect on the image if the object is moved from infinity towards the focus of a convex lens?
What is the formula for the magnification (m) produced by a lens in terms of image height (h') and object height (h)?
What is the nature of the image formed by a convex lens when the object is placed between the focus and the optical center?
What is the principal axis of a lens?
What is the sign convention for the focal length of a convex lens?
What is the unit of power of a lens?