Question

I have a excercise for Optics. Help me. Thank a lot

Question 2 (3.00pts) 2.1 (1.00pt) How can you determine the direction of the polarizing axis of a single polarizer provided that you have a known polarizer with a marked axis? 2.2 (1.00pt) The focal length of a simple lens depends on the color of light passing through it. Why? Is it possible for a lens to have a positive focal length for some colors and negative for others? Explain. 2.3(1.00pt)Could x-ray diffraction effects with crystals be observed by using visible light instead of X- rays? Why or why not?

Answer 1

2.1 the polarizing axis of a single polarizer can be determined is to use a reflection from water , shiny/glossy floor which lies near Brewster angle which makes the light strongly polarized in the plane of reflecting surface.

it can be explained as

Hold the polarizing lens at varying distance to the table surface

keep it stable when it focuses and then turn it in reference to the light source . a brighter focus and polarization lines can be seen when polarizing axis is matched with lens and color of light .

2.2

The formula of focal length has factor n , as n varies with color focal length changes

No a lens cannot have positive focal length for few colors and negative for others n. since C is a universal speed limit n< 1 is impossible . to change for positive for few color and negative for others n should change its sign n >1 for some color and n< 1 for others which is not possible

2.3 answer is not possible with visible light.

X-Rays diffraction patters used for determine the crystalline arrangement of atoms inside atoms inside a solid are only possible if the wave length of radiation are comparable to or smaller than the separations of atoms themselves . where as visible light wavelength are thousand times longer then the separation of atoms in solid so diffraction of visible light cannot occur . the visible light is either transmitted through solid or either reflected or absorbed.