A transparent material bounded by two surfaces, of which one or both surfaces are spherical, form a lens. [A lens is bound by at least one spherical surface. In such lenses, the other surface would be plane.]
With respect to air, the refractive index of ice is $1.31$ and that of rock salt is $1.54$. Calculate the refractive index of rock salt with respect to ice.
Answer
$n _{ ia }=1.31 \text { and } n _{ ra }=1.54, n _{ ri }=\text { ? }$
$\text { Now, } N _{ ri }=\frac{n_{r a}}{n_{ ia }}=\frac{1.54}{1.31}=1.17$
For the same angle of incidence in media $P, Q$ and $R$, the angles of refraction are $45^o$, $35^o$ and $30^o$ respectively. In which medium is the speed of light minimum? Give reason for your answer.
Answer
In medium $R$, the speed of light is minimum.
In the usual notation, as $n =\frac{c}{v}=\frac{\sin i}{\sin r}$
For medium $R$, r is minimum and hence the speed $v$ is minimum.
Which property of a concave mirror is utilized for using it as a shaving mirror?
Answer
When an object is held between the pole and the principal focus of a concave mirror, a virtual, erect and magnified image of the object is formed. This property of a concave mirror is utilized for using it as a shaving mirror.
Explain briefly. why a ray of light passing through the centre of curvature of a concave mirror, gets reflected along the same path.
Answer
The ray of light passing through the centre of curvature of a concave mirror is incident on the mirror along its normal. So, i =r=0. Therefore, the ray retraces its path.
A person got his eyes tested by an optician. The prescription for the spectacle lenses to be made reads : Right eye:$ +2.00 D$, Left eye: $+2.50 D$ $(a)$ State whether these lenses are thicker in the middle or at the edges. $(b)$ State whether these spectacle lenses will converge light rays or diverge light rays.
The optician's prescription for a pair of spectacles is: Right eye:$ -3.50 D,$ Left eye: $-4.00 D (a)$ Are these lenses thinner at the middle or at the edges? $(b)$ Which is the weaker eye?
Which causes more bending (or more refraction) of light rays passing through it: a convex lens of long focal length or a convex lens of short focal length?
The refractive index of glass with respect to air is $3/2$. The refractive index of air with respect to the glass is $4/6.$ Do you agree with this statement?
What sign [+ve (plus) or -ve (minus)] has been given to the following on the basis of the New Cartesian sign convention? $(a)$ Height of a real image and $(b)$ Height of a virtual image?
A student traces the path of a ray of light passing through a rectangular glass slab and marks the angle of incidence $i$, angle of refraction $r$ and angle of emergence $e$, as shown in the figure :
When a parallel beam of light falls on a rough surface, the light is reflected in different directions. This type of reflection is known as diffused reflection.