an object is placed on the principal Axis at a distance of 8 cm in front of a concave mirror of focal length 3 cm draw ray diagram to find the image write the chapters of the image formed
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Ray-drawing has a big disadvantage: it can walk off the page very easily indeed.
First, you're describing a make-up or shaving mirror which has a magnified erect image that is virtual (on the dull side of the mirror.
Therefore don't start with the mirror in the middle of the page. Start with object quite close to edge and draw 2 (or indeed all 3) of the rays from tip of object.
a) parallel to axis, reflecting through F
b) through F reflecting parallel to axis
c) to the pole, where it acts like a plane mirror and i = r
These backtrack (dotted lines) to locate the tip of the image.
Of course it helps if you use The Formula (I use Real Is Positive convention)
1/u + 1/v = 1/f
1/v = 1/f - 1/u = 1/10 - 1/8 = 4/40 - 5/40 = -1/40
v = -40 (which means virtual, behind the mirror in this convention)
M = v/u = -40/8 = -5 (which means 5x and erect)
So it's quite easy to “cheat" by drawing your object (say) 2cm tall, 8cm in front of the mirror and the image 10cm tall and 40cm behind, then Bob's your uncle, the rays draw themselves.
First, you're describing a make-up or shaving mirror which has a magnified erect image that is virtual (on the dull side of the mirror.
Therefore don't start with the mirror in the middle of the page. Start with object quite close to edge and draw 2 (or indeed all 3) of the rays from tip of object.
a) parallel to axis, reflecting through F
b) through F reflecting parallel to axis
c) to the pole, where it acts like a plane mirror and i = r
These backtrack (dotted lines) to locate the tip of the image.
Of course it helps if you use The Formula (I use Real Is Positive convention)
1/u + 1/v = 1/f
1/v = 1/f - 1/u = 1/10 - 1/8 = 4/40 - 5/40 = -1/40
v = -40 (which means virtual, behind the mirror in this convention)
M = v/u = -40/8 = -5 (which means 5x and erect)
So it's quite easy to “cheat" by drawing your object (say) 2cm tall, 8cm in front of the mirror and the image 10cm tall and 40cm behind, then Bob's your uncle, the rays draw themselves.
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