To ensure almost `100%` transmittivity, photographic lenses are often coated with a thin layer of dielectric maerial, like `MgF_(2)(mu=1.38)` . The minimum thickness of the film to be used so that at the centre of visible spectrum `(lambda = 5500 Å)` there is maximum transmission.A. `1000Å`B. `2000Å`C. `4000Å`D. 500Å`

To ensure almost `100%` transmittivity, photographic lenses are often

1.	To ensure almost `100%` transmittivity, photographic lenses are often coated with a thin layer of dielectric maerial, like `MgF_(2)(mu=1.38)` . The minimum thickness of the film to be used so that at the centre of visible spectrum `(lambda = 5500 Å)` there is maximum transmission.A. `1000Å`B. `2000Å`C. `4000Å`D. 500Å`
Answer» Correct Answer - A for interfrence at thin films `(2mu cosd r) = (lambda)/(2)` Here `i~~r~~0` `:. T = (lambda)/(4mu)`

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Angular width of central maxima in the Fraunhofer diffraction pattern of a slit is measured. The slit is illuminated by light of wavelength `6000Å`. When the slit is illuminated by light of another wavelength, the angular width decreases by 30%. The wavelength of this light will beA. `3500 Å`B. `4200 Å`C. `4700 Å`D. `6000 Å`
Find the half angular width of the central bright maximum in the fraunhofer diffraction pattern of a slit of width `12xx10^(-5)cm` when the slit is illuminated by monochromatic light of wavelength 6000 Å.
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Light wavelength 6000 Å is incident normally on a slit of width `24xx10^(-5)` cm. find out the angular position of seconds minimum from central maximum?

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