Fill in the following blanks with suitable words :
A person is short-sighted if his eyeball is too………….Spectacles with a ………….lens are needed. A person is long-sighted if his eyeball is too………. Spectacles with a……………….lens are needed. These focus light rays exactly on to the................

Fill in the following blanks with suitable words: If a person is doing exercise, his breathing rate …………..

Fill in the following blanks with suitable words : A concave lens ___________ parallel rays of light whereas a convex lens _____________ parallel rays of light.

Fill in the following blanks with suitable words: a) Parallel rays of light are refracted by a convex lens to a point called the…………… b) The image in a convex lens depends uponthe distance of the ……………. From the lens.

Fill in the following blanks with suitable words : (a) Most of the refraction of light rays entering the eye occurs at the outer surface of the…………….. (b) The part of eye sensitive to light is…………… (c) The part of eye which alters the size of the pupil is................ (d) When light is dim, the pupil becomes..................... (e) The iris controls the amount of................entering the eye. (f) The ciliary muscles control the shape of the................................ (g) To bring light from a distant object to a focus on the retina of the eye, the convex eye-lens needs to be made............. (h) To bring light from a near object to a focus on the retina of the eye, the convex eye-lens needs to be made............

Fill in the following blanks with suitale words: A) A convex lens ……………….. Rays of light, whereas a concave lens …………… rays of light. b) Lenses refract light to form images, a…………………. Lens can form both real and virtual images, but a diverging lens forms only.................images.

A short sighted person cannot see clearly beyond 2m. Caclulate the power of lens required to correct his vision.

A short sighted person cannot see clearly beyond 2 m . Calculate power of the lens required to correct his eye to normal vision.

(a) What is long-sightedness ? State the two causes of long-sightedness (or hypermetropia). With the help of ray diagrams, show : (i) the ray-defect long-sightedness. (ii) correction of long-sightedness by using a lens. (b) What eye has a near point distance of 0.75 m. What sort of lens in spectacles would be needed to reduce the near point distance to 0.25 m ? Also calculate the power of lens required. Is this eye long-sighted or short-sighted ? An eye has a far point of 2 m. What type of lens in spectacles would be needed to increase the far point to infinity ? Also calculate the power of lens required. Is this eye long-sighted or short-sighted ?

A short sighted person can see distinctly only those objects which lie between 10 cm and 100 cm from him. The power of the spectacle lens required to see a distant object is