Why the colour of the Ocean appears blue?

Why the colour of the Ocean appears blue?

A. Because the sunlight falling on it is scattered.
B. Because the sunlight falling on it is absorbed.
C. Because the sunlight falling on it is refracted.
D. Because the sunlight falling on it is reflected.

“The ocean looks blue because red, orange and yellow (long wavelength light) are absorbed more strongly by water than is blue (short wavelength light). So when white light from the sun enters the ocean, it is mostly the blue that gets returned. Same reason the sky is blue.”

The distance between the optical centre of a convex lens and its principal focus is called its_______?

The distance between the optical centre of a convex lens and its principal focus is called its_______?

A. Focal Length
B. Radius of Curvature
C. Power
D. Magnification

The distance between the optical centre and principal focus of a lens is called focal length. Focal length of a lens depends on the refractive index of the glass and its curvature.

A convex mirror always ___________ ?

A convex mirror always ___________ ?

A. Forms a real image
B. Forms a virtual image 
C. Forms an inverted image
D. Produces a larger image

In convex mirrors light rays from a point always gets diverged (they dont meet at any point). So we have to extend them behind the mirror so that they appear to meet. Since image is formed behind of mirror, they cant be received on screen. So it is not real image. Thus it is a virtual image.

Which among the following types of lenses are prescribed by doctors for a patient suffering from astigmatism?

Which among the following types of lenses are prescribed by doctors for a patient suffering from astigmatism?

A. Cylindrical Lens  
B. Concave Lens
C. Spherical Lens
D. Convex Lens

Astigmatism is a common vision problem caused by an error in the shape of the cornea. With astigmatism, the lens of the eye or the cornea, which is the front surface of the eye, has an irregular curve. This can change the way light passes, or refracts, to your retina. This causes blurry, fuzzy, or distorted vision.
A cylindrical lens is a lens which focuses light into a line instead of a point, as a spherical lens would. The curved face or faces of a cylindrical lens are sections of a cylinder, and focus the image passing through it into a line parallel to the intersection of the surface of the lens and a plane tangent to it.

Dioptre is a unit of measurement for __________ ?

Dioptre is a unit of measurement for __________ ?

A. Current
B. Lens
C. Force
D. Focal Length

A dioptre is a unit of measurement of the optical power of a lens or curved mirror, which is equal to the reciprocal of the focal length measured in metres. (1 dioptre = 1 m−1.) It is thus a unit of reciprocal length.