• Sunday, March 25, 2012

    Retinal Fatigue

    Syed Masoom Rizvi
    Q: What is retinal fatigue?
    A: When white object is seen after looking a bright object for a long time it does not appear its original colour. Its appear with black strips.It is due to retinal fatigue. On looking bright object eyes sensitized which unaffected by low intensity. When white object is seen after viewing a red spot for a long time then its appear greenish indigo because it is complementary colour of red.

    Define Brewster's Law

    Syed Masoom Rizvi
    Q: Explain Brewster's Law.
    Brewster's Law DiagramA: Let us take a glass slab of refracting index "μ". When the angle between refracted ray and reflected ray is 90˚ then both the ray should polarised.

    i + r = 90˚
    r = 90 - i
    Brewster's Law

    This law is called Brewster's Law.

    Power of A Lens

    Syed Masoom Rizvi
    Q: What do you mean by power of a lens?
    A: The power of deviating of a ray of light by a lens is inversely proportional to the focal length of the lens.
    It is the power which is known as the power of lens. It is given by P=1/f. Its S.I. unit is diopter.
    It is a characteristic of lens which does not depend upon distance of object(u) and distance of image(v). It is the sum of the powers of its refracting surface.