Help with optics physics questions please?

The index of refraction of a certain glass is 1.50. The sine of the critical angle for total


internal reflection at the glass-air interface is: (nair = 1)


A 0.50


B 0.67


C 0.75


D 1.00


E 1.50





Where must an object be placed in front of a converging lens in order to obtain a virtual


image?


A at the focal point


B at twice the focal length


C greater than the focal lengthy


D between the focal point and the lens


E between the focal length and twice the focal length





An erect object placed outside the focal point of a converging lens will produce an image


that is:


A erect and virtual


B inverted and virtual


C erect and real


D inverted and real


E impossible to locate





An ordinary magnifying glass in front of an erect object produces an image which is:


A real and erect


B real and inverted


C virtual and inverted


D virtual and erect


E none of these





Thank-you to all that take the time to help me