www.bbcnoun.com.ng A far-sighted person cannot see objects that are less than 100cm away. If he is to read a book at 25cm, recommend the type and focal length of the lens the person will need Concave and 33cm Which of the following is NOT an example of diffraction? Hearing the seeker shout 'ready', when you are behind a tree A concave mirror has focal length 40 cm, how far should the mirror be placed in order to give an image of two fold magnification of the an object? 60.0cm When light travels in a certain medium and falls on the surface of another medium, a part of it turns back in the same medium. This phenomenon is called __ Refraction The variation of focal length to form a sharp image on retina is called __ Accommodation A ray of light parallel to the principal axis of the mirror upon reflected by the mirror passes through __ the principal focus The greatest angle on a prism for which emergent rays can still be obtained it is called _ limiting angle In which of the following instruments is the focal length of the objective lens larger than that of the eyepiece? Telescope The maximum deviation of light by a prism occurs when the angle of incidence is __ 90 Degrees The lens with a long focal length is _ thin and not strongly curved