NEET-XII-Physics
17: Light Waves
- #7-aFind the distance of the centre of the first minimum from the centre of the central maximum. (b) How many bright fringes are formed in one centimetre width on the screen? (b) How many bright fringes are formed in one centimetre width on the screen?Ans : The distance of the centre of the first minimum from the centre of the central maximum, x = `` \frac{\,\mathrm{\,width\,}\,\mathrm{\,of\,}\,\mathrm{\,central\,}\,\mathrm{\,maxima\,}}{2}``
That is, `` x=\frac{\beta }{2}=\frac{\lambda D}{2d}`` ...(i)
`` =\frac{5\times {10}^{-7}\times 1}{2\times {10}^{-3}}``
`` =2.5\times {10}^{-4}\,\mathrm{\,m\,}=0.25\,\mathrm{\,mm\,}`` (b) From equation (i),
fringe width, `` \beta =2\times x=0.50\,\mathrm{\,mm\,}``
So, number of bright fringes formed in one centimetre (10 mm) = `` \frac{10}{0.50}=20``.
Page No 381: (b) From equation (i),
fringe width, `` \beta =2\times x=0.50\,\mathrm{\,mm\,}``
So, number of bright fringes formed in one centimetre (10 mm) = `` \frac{10}{0.50}=20``.
Page No 381:
- #7-bHow many bright fringes are formed in one centimetre width on the screen?Ans : From equation (i),
fringe width, `` \beta =2\times x=0.50\,\mathrm{\,mm\,}``
So, number of bright fringes formed in one centimetre (10 mm) = `` \frac{10}{0.50}=20``.
Page No 381: