OL 1 Flashcards
why do light rays bend (refract)
glass is denser than air
speed of light slows down as density of the transparent medium increases
define refractive index
velocity of light in a vacuum / velocity of light in the material
why is n always greater than 1
all transparent media slow down the speed of light, thus n is always greater than 1
what is the refractive index of air, water, spectacle crown glass, plastic (CR39)
air= 1
water= 1.333
spectacle crown glass= 1.523
plastic (cr39)= 1.498
whats dispersion
when white light is split into its constituent components by a transparent refracting medium
the speed of light varies for each wavelength
wavelength range of visible spectrum ?
380nm- 780nm
what colour is long, medium and short wavelengths?
red (long)
green/yellow (medium)
blue (short)
fill blanks:
____ _____ is dependent on the wavelength of light so the _____ of light when defining ____ ____ must be specified
refractive index
wavelength
refractive index
how is refractive index defined?
using reference spectral wavelengths derived from the absorption spectra (fraunhofer lines) of different elements
define absorption spectrum?
why can u see dark lines?
the characteristic pattern of dark lines that occurs when the electromagnetic spectrum is passed through a gas or liquid and recorded by a spectroscope.
The dark lines are due to the absorption of photons of light by atoms and therefore each element in gaseous or liquid form has a unique spectrum.
how can astronomers deduce which elements are present?
observing the suns spectrum of Fraunhofer lines.
what is the wavelength of -(helium “d” line , UK)
mercury “e” line, France/germany
helium “d” line , UK= 587.562nm
mercury “e” line, France/germany= 546.073nm
why can you see the spectral line showing the specific wavelengths of helium and mercury on the emission spectrum?
corresponds close to the wavelengths that the human eye is most sensitive to in daylight (photopic conditions) i.e. the photopic sensitivity curve.
what happens as you increase the refractive index of the transparent material used to manufacture lens?
the thinner the lens will be
2 laws of refraction are?
1- the incident light ray, the refracted ray and the normal to the surface at the point of incidence all lie in one plane
2- the ratio of the sine of the angle of incidence, i, to the sine of the angle of refraction, i’, is constant for any two media
