F.3 LIGHT 4個問題..好難

※絕~§影§~※

1.有無人知點DRAW PLANE MIRROR, CURVED MIRRORS 同CONCAVE MIRROR 的RAW DIAGRAM??好難..

2.A student stands at centre of classroom with dimension 10m X 10m X 10m as shown in the diagram below:


If he wants to use of a plane mirror, hanging in front of him,so as to see the backside wall of the classroom.
What should be the minimum size of the mirror to buy?

3.A person looks at an illuminated letter 'J' b using the periscope shown. Sketch the image as observed by him.


4.A person looks at an illuminated letter 'J' b using the periscope shown. Sketch the image as observed by him.


我唔係想要個ANS..係要知點解@@

LMLM.^.

有冇中文版-.-
3應該係 正立 虛像
4係 倒立 虛像

[ 本帖最後由 LMLM.^. 於 13-4-2008 17:00 編輯 ]

Zend

2A. 用幾何學上應該係高度一半
concave mirror convex mirror 連A-level 都out-c , sigh =.=
不過你上網找d 資料都唔係太難
3-.-你自己畫圖啦, 唔好懶

[S]【YU】

curved mirror 應該 out-C 了.
好難用文字解,自己睇wiki d 圖思考下啦
http://en.wikipedia.org/wiki/Curved_mirror

plane mirror 只要跟返law of reflection就得
http://en.wikipedia.org/wiki/Law_of_reflection


mirror size = 2 x CD
tri ACD and triACB are conguent  triangle (ASA)
BC = CD ( corr. sides)
tri ACB and triAEF are similar triagle (AAA)
BC/(5-CD) = 5/10
CD = 5/3
size = 5/3x2 = 3.33m

(i) the right way up J
(ii) unside down J

※絕~§影§~※

原帖由 LMLM.^. 於 13-4-2008 16:54 發表
有冇中文版-.-
3應該係 正立 虛像
4係 倒立 虛像

點樣先至知佢係正立 虛像 定倒立 虛像
就係唔知點樣C-  -

※絕~§影§~※

原帖由 Zend 於 13-4-2008 17:20 發表
2A. 用幾何學上應該係高度一半
concave mirror convex mirror 連A-level 都out-c , sigh =.=
不過你上網找d 資料都唔係太難
3-.-你自己畫圖啦, 唔好懶

3...就係唔識畫-  -

LMLM.^.

4.直畫過去反射再反射  兩條線上下反轉了
3就係反射再反射 線冇轉

[ 本帖最後由 LMLM.^. 於 13-4-2008 18:10 編輯 ]

※絕~§影§~※

原帖由 [S]【YU】 於 13-4-2008 17:27 發表
curved mirror 應該 out-C 了.
好難用文字解,自己睇wiki d 圖思考下啦
http://en.wikipedia.org/wiki/Curved_mirror

plane mirror 只要跟返law of reflection就得
http://en.wikipedia.org/wiki/Law_of_reflec ...

WHY mirror size = 2 x CD
AND HOW DO U KNOW個2到係  5M??

[S]【YU】

WHY mirror size = 2 x CD

because i am just calculating half of the mirror which allows the ppl to watch the RHS of the wall behind. LHS is just the same, so x2 afterward.

AND HOW DO U KNOW個2到係  5M??

center of the room.

※絕~§影§~※

原帖由 [S]【YU】 於 13-4-2008 19:00 發表

because i am just calculating half of the mirror which allows the ppl to watch the RHS of the wall behind. LHS is just the same, so x2 afterward.


center of the room.

I mean the position of the mirror.
EA is the incident ray from the object
AD is the reflected ray.
So, why the mirror cannot be CD??
It can allow EA to enter the mirror and reflected to let us see.
???Sorry, my concept is really bad.