ऑन द बेसिस ऑफ हाइगेंस वेव थिअरी आफ लाइट थ्रू द सिटी इन लाइट ऑन मीडियम इज ग्रेटर द सिटी ऑफ लाइट इन डेंजर मीडियम
Answers
Answer:
Answer
Consider a plane wavefront of monochromatic light obliquely incident at a plane refracting surface PQ separating two mediums. Let A
1
B
1
and AB be successive positions of the incident wavefront one wavelength apart and A
1
A and B
1
B, the corresponding incident rays. Let v
1
and v
2
be the speed of light in medium (1) and medium (2) respectively. If 't' is the time taken by the incident ray to cover the distance BC, then BC=v
1
t. During this time the secondary wavelets originating at A cover a distance v
2
t in the denser medium. With A as centre draw a hemisphere of radius v
2
t in the denser medium. It represents the secondary wavefront originating at A. Draw a tangent CD to the secondary wavefront. As all points on CD are in same phase of wave motion, CD represents the refracted wavefront in the denser medium.
So BC=v
1
t
and AD=v
2
t
In ΔABC sini=
AC
BC
In ΔACD sinr=
AC
AD
sinr
sini
=
AD/AC
BC/AC
=
AD
BC
=
v
2
t
v
1
t
sinr
sini
=
v
2
v
1
as i>r
So sini>sinr
and because
1
μ
2
>1
So v
1
>v
2
i.e., velocity of light in a rarer medium is greater than the velocity of light in denser medium.
Explanation: