optics..

[yingao]

which of the following is not true concerning ray diagrams?

a. all horizontal ligth rays reflect through the focacl point of any lens or mirror
b. light rays striking the center of a thin lens move straight through the lens
c. light rays coming through the focal point and striking a mirror are reflected horizontally
d. light rays coming though the focal point and striking a convex lens are refracted through the second focal point..

ans:Ｄ，can someone explain why D is wrong. Thx!!

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[Majik]

which of the following is not true concerning ray diagrams?

a. all horizontal ligth rays reflect through the focacl point of any lens or mirror
b. light rays striking the center of a thin lens move straight through the lens
c. light rays coming through the focal point and striking a mirror are reflected horizontally
d. light rays coming though the focal point and striking a convex lens are refracted through the second focal point..

ans:Ｄ，can someone explain why D is wrong. Thx!!

A, B, and C are all true statements. D is false because a light ray coming through the focal point of a lens passes directly through horizontally without being refracted. In fact, if the light ray refracted, it wouldn't pass through the second focal point. Conceptually, the reason why the light ray isn't refracted even though it's passing through a different medium is because the angle of incidence (with respect to normal line) is zero. Therefore the angle of refraction is also zero. Here's a crappy image I drew that might help:

 

[yingao]

A, B, and C are all true statements. D is false because a light ray coming through the focal point of a lens passes directly through horizontally without being refracted. In fact, if the light ray refracted, it wouldn't pass through the second focal point. Conceptually, the reason why the light ray isn't refracted even though it's passing through a different medium is because the angle of incidence (with respect to normal line) is zero. Therefore the angle of refraction is also zero. Here's a crappy image I drew that might help:

Thank you so much.. I really appreciated your drawing!!!