1. The distance between optic centre and principal focus of the lens is known as
The distance between the optic center and the principal focus of a lens is known as the focal length. It is a key property of the lens that determines its focusing ability.
2. The position of the object in a compound microscope is
In a compound microscope, the object is typically placed between the focal point (F) and twice the focal point (2F) of the objective lens to form an enlarged image.
3. A convex lens does not produce a
A convex lens can produce virtual, magnified images when the object is placed within the focal length, but it cannot produce a virtual diminished image. Virtual images formed by a convex lens are typically magnified.
4. The total internal reflection prisms are used in
Total internal reflection prisms are used in a periscope to redirect light and allow for viewing over obstacles. This principle is also applied in other optical devices, but it's most commonly associated with periscopes.
5. Which of the following are primary colours?
These are the primary colors of light used in the additive color model, where various combinations of red, green, and blue light create other colors.
6. When magenta, yellow and cyan are added, the colour obtained is
Magenta, yellow, and cyan are the primary colors in the subtractive color model. When combined in equal proportions, they absorb all the wavelengths of light, resulting in the color white.
7. When a ray of light passes from a denser to rarer medium, the reflected ray is
When a ray of light passes from a denser to a rarer medium (e.g., from water to air), it bends away from the normal due to a decrease in the speed of light. This is a result of refraction.
8. For total internal reflection the angle of incidence is
For total internal reflection to occur, the angle of incidence must be greater than the critical angle. When the angle of incidence exceeds the critical angle, all the light is reflected back into the denser medium, rather than refracting into the rarer medium.
9. If an object absorbs all colours, it appears
An object that absorbs all colors of light appears black because it does not reflect or transmit any light, absorbing all wavelengths in the visible spectrum.
10. In the human being, the part which is sensitive to light is
he retina is the light-sensitive part of the human eye. It contains photoreceptor cells (rods and cones) that detect light and send signals to the brain to form images.
11. The angle of incidence for which the angle of refraction is 90° is called as
The critical angle is the angle of incidence at which the angle of refraction becomes 90°. This phenomenon occurs when light travels from a denser medium to a rarer medium, and total internal reflection happens.
12. The refractive index of Benzene is
The refractive index of benzene is 1.50, indicating light slows down and bends more when passing from air into benzene. This property is linked to the optical density of the substance.
13. A fixed point lying in between the two spherical surfaces through which a ray of light passing suffers no deviation is
The optic center is the point inside a lens where light passing through it suffers no deviation. It lies between the two spherical surfaces of the lens, unaffected by refraction.