Explain the refraction of a plane wavefront by a thin convex lens.
(N/A) The figure shows a plane wavefront $XY$ of a parallel beam of light incident on a thin convex lens. The rays emerging from the lens are concentrated at the second focus point $F$.
To draw the refracted wavefront corresponding to these rays,we draw an arc of a circle centered at the focus $F$. The arc $X^{\prime}Y^{\prime}$ shown in the figure represents this wavefront at a specific instant.
In this process,the path length traveled by the light ray passing through the center of the lens (point $B$ to $b$) is greater than the path length traveled by the rays passing through the edges (points $A$ to $a$ and $C$ to $c$). Since the speed of light in the lens material is less than in air,the central part of the wavefront is delayed more than the edges. Consequently,the point $b$ on the wavefront lags behind points $a$ and $c$,resulting in a spherical converging wavefront.
To draw the refracted wavefront corresponding to these rays,we draw an arc of a circle centered at the focus $F$. The arc $X^{\prime}Y^{\prime}$ shown in the figure represents this wavefront at a specific instant.
In this process,the path length traveled by the light ray passing through the center of the lens (point $B$ to $b$) is greater than the path length traveled by the rays passing through the edges (points $A$ to $a$ and $C$ to $c$). Since the speed of light in the lens material is less than in air,the central part of the wavefront is delayed more than the edges. Consequently,the point $b$ on the wavefront lags behind points $a$ and $c$,resulting in a spherical converging wavefront.
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$A$ light wave travels in a vacuum along the $x$-axis. Which of the following may represent the wave front?
Easy
View SolutionThe figure shows a surface $XY$ separating two transparent media,medium-$1$ and medium-$2$. The lines $ab$ and $cd$ represent wavefronts of a light wave travelling in medium-$1$ and incident on $XY$. The lines $ef$ and $gh$ represent wavefronts of the light wave in medium-$2$ after refraction.
$1.$ Light travels as a
$(A)$ parallel beam in each medium
$(B)$ convergent beam in each medium
$(C)$ divergent beam in each medium
$(D)$ divergent beam in one medium and convergent beam in the other medium.
$2.$ The phases of the light wave at $c, d, e$ and $f$ are $\phi_{c}, \phi_{d}, \phi_{e}$ and $\phi_{f}$ respectively. It is given that $\phi_{c} \neq \phi_{f}$.
$(A)$ $\phi_{c}$ cannot be equal to $\phi_{d}$
$(B)$ $\phi_{a}$ can be equal to $\phi_{e}$
$(C)$ $(\phi_{d}-\phi_{c})$ is equal to $(\phi_{f}-\phi_{e})$
$(D)$ $(\phi_{d}-\phi_{c})$ is not equal to $(\phi_{f}-\phi_{e})$
$3.$ Speed of the light is
$(A)$ the same in medium-$1$ and medium-$2$
$(B)$ larger in medium-$1$ than in medium-$2$
$(C)$ larger in medium-$2$ than in medium-$1$
$(D)$ different at $b$ and $d$
Give the answer for questions $1, 2$ and $3$.
$1.$ Light travels as a
$(A)$ parallel beam in each medium
$(B)$ convergent beam in each medium
$(C)$ divergent beam in each medium
$(D)$ divergent beam in one medium and convergent beam in the other medium.
$2.$ The phases of the light wave at $c, d, e$ and $f$ are $\phi_{c}, \phi_{d}, \phi_{e}$ and $\phi_{f}$ respectively. It is given that $\phi_{c} \neq \phi_{f}$.
$(A)$ $\phi_{c}$ cannot be equal to $\phi_{d}$
$(B)$ $\phi_{a}$ can be equal to $\phi_{e}$
$(C)$ $(\phi_{d}-\phi_{c})$ is equal to $(\phi_{f}-\phi_{e})$
$(D)$ $(\phi_{d}-\phi_{c})$ is not equal to $(\phi_{f}-\phi_{e})$
$3.$ Speed of the light is
$(A)$ the same in medium-$1$ and medium-$2$
$(B)$ larger in medium-$1$ than in medium-$2$
$(C)$ larger in medium-$2$ than in medium-$1$
$(D)$ different at $b$ and $d$
Give the answer for questions $1, 2$ and $3$.
Huygens' principle of secondary wavelets may be used to
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View SolutionWhat is visible light? Write various views on it.
Easy
View SolutionAccording to Huygens principle, the phase difference between oscillations of any two particles on the same wave front is . . . . . . rad.
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