Tbr cbt 3 q51

[greenseeking]

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In 1990, the Hubble Space Telescope (HST) was placed in orbit above the Earth. The HST has a primary concave mirror that is 2.4 meters in diameter, designed to let astronomers see into a volume of space about 400 times larger than that permitted by other optical systems currently available. Compared to the object being observed, the image formed by the primary mirror of the HST is:

A. real, inverted, and smaller.
B. real, erect, and smaller.
C. virtual, inverted, and smaller.
D. virtual, erect, and larger.

Answer is A.

So, I got this question right by guessing and figuring out that r=1.2m, f=0.6m, etc... but I was wondering if someone could explain to me where the astronomer/Earth is in relation to the object and the mirror. Where is the object? In the answer key it said that the object is in between the earth and the mirror. But how would we know where the object is?

EARTH--------------object----------------- mirror/Telescope ?

or

EARTH-----------------mirror/telescope-------------------- object ?

 

[circulus vitios]

I'm not sure why you need to know any of that? Just draw a really quick ray diagram. http://www.physicsclassroom.com/class/refln/u13l3d.cfm The object is a celestial object so it's going to be incredibly far away, relative to the mirror diameter and the focal point.

 

[greenseeking]

Yeah I see your point but the thing is, if it is so far away, shouldn't it be

earth-------mirror------ object, so that the mirror is no longer concave? object has to be in the inner curved portion of the mirror right and the person viewing has to be at the same side.