7. What is lens? Distinguish between convex and a concave lens.
1. Short-answer type questions (II):
1. (a) What is Newton's colour disk? What is its application?
(b) Which type of lens forms always a virtual image?
(c) Name the lens which produce real images.
2. (a) Give two differences between real image and virtual image.
(b) Give two differences between convex mirror and concave mirror.
3. (a) In what kind of surfaces can we see a clear reflected image of an object?
(b) Give one method of splitting up white light into its constituent colours.
4. (a) Draw a neat diagram for the formation of an image in plane mirror when a pencil is placed in front of it
(b) What is the principle of image formed in the plane mirror?
R. Long-answer
Answers
Answer:
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Answer:
7. ᴀ ᴄᴜʀᴠᴇᴅ ᴘɪᴇᴄᴇ ᴏғ ɢʟᴀss ᴛʜᴀᴛ ᴍᴀᴋᴇs ᴛʜɪɴɢs ʟᴏᴏᴋ ʙɪɢɢᴇʀ, ᴄʟᴇᴀʀᴇʀ, ᴇᴛᴄ. ᴡʜᴇɴ ʏᴏᴜ ʟᴏᴏᴋ ᴛʜʀᴏᴜɢʜ ɪᴛ.
ᴀ ᴄᴏɴᴠᴇx ʟᴇɴs ᴏʀ ᴄᴏɴᴠᴇʀɢɪɴɢ ʟᴇɴs ғᴏᴄᴜsᴇs ᴛʜᴇ ʟɪɢʜᴛ ʀᴀʏs ᴛᴏ ᴀ sᴘᴇᴄɪғɪᴄ ᴘᴏɪɴᴛ ᴡʜᴇʀᴇᴀs ᴀ ᴄᴏɴᴄᴀᴠᴇ ʟᴇɴs ᴏʀ ᴅɪᴠᴇʀɢɪɴɢ ʟᴇɴs ᴅɪᴠᴇʀɢᴇs ᴛʜᴇ ʟɪɢʜᴛ ʀᴀʏs. ᴡʜᴇɴ ᴛʜᴇsᴇ ʟᴇɴsᴇs ᴀʀᴇ ᴄᴏᴍʙɪɴᴇᴅ, ᴛʜᴇʏ ᴘʀᴏᴅᴜᴄᴇ sʜᴀʀᴘᴇʀ ɪᴍᴀɢᴇs.
1. (ᴀ) ᴛʜᴇ ɴᴇᴡᴛᴏɴ's ᴄᴏʟᴏᴜʀ ᴡʜᴇᴇʟ/ᴅɪsᴋ ɪs ᴜsᴇᴅ ғᴏʀ ᴅᴇᴍᴏɴsᴛʀᴀᴛɪɴɢ ʜᴏᴡ ᴡʜɪᴛᴇ ʟɪɢʜᴛ ɪs ᴄᴏᴍᴘᴏsᴇᴅ ᴏғ ᴛʜᴇ ᴄᴏʟᴏᴜʀs ᴏғ ᴛʜᴇ ʀᴀɪɴʙᴏᴡ. sᴏᴍᴇ ᴡʜɪᴛᴇ ɪs ᴀʟsᴏ ᴘʀᴇsᴇɴᴛ ғᴏʀ ᴀ ʙᴇᴛᴛᴇʀ ʀᴇsᴜʟᴛ ᴡʜᴇɴ ᴠɪᴇᴡɪɴɢ ᴛʜᴇ ʀᴏᴛᴀᴛɪɴɢ ᴅɪsᴋ.
(ʙ) ᴀ ᴄᴏɴᴄᴀᴠᴇ ʟᴇɴs ғᴏʀᴍs ᴀ ᴠɪʀᴛᴜᴀʟ ɪᴍᴀɢᴇ.
(ᴄ) ᴄᴏɴᴠᴇx (ᴄᴏɴᴠᴇʀɢɪɴɢ) ʟᴇɴsᴇs ᴄᴀɴ ғᴏʀᴍ ᴇɪᴛʜᴇʀ ʀᴇᴀʟ ᴏʀ ᴠɪʀᴛᴜᴀʟ ɪᴍᴀɢᴇs (ᴄᴀsᴇs 1 ᴀɴᴅ 2, ʀᴇsᴘᴇᴄᴛɪᴠᴇʟʏ), ᴡʜᴇʀᴇᴀs ᴄᴏɴᴄᴀᴠᴇ (ᴅɪᴠᴇʀɢɪɴɢ) ʟᴇɴsᴇs ᴄᴀɴ ғᴏʀᴍ ᴏɴʟʏ ᴠɪʀᴛᴜᴀʟ ɪᴍᴀɢᴇs (ᴀʟᴡᴀʏs ᴄᴀsᴇ 3). ʀᴇᴀʟ ɪᴍᴀɢᴇs ᴀʀᴇ ᴀʟᴡᴀʏs ɪɴᴠᴇʀᴛᴇᴅ, ʙᴜᴛ ᴛʜᴇʏ ᴄᴀɴ ʙᴇ ᴇɪᴛʜᴇʀ ʟᴀʀɢᴇʀ ᴏʀ sᴍᴀʟʟᴇʀ ᴛʜᴀɴ ᴛʜᴇ ᴏʙᴊᴇᴄᴛ.
2. (ᴀ)ʀᴇᴀʟ ɪᴍᴀɢᴇs ᴀʀᴇ ғᴏʀᴍᴇᴅ ᴡʜᴇɴ ʟɪɢʜᴛ ʀᴀʏs ᴀғᴛᴇʀ ʀᴇғʟᴇᴄᴛɪᴏɴ ᴏʀ ʀᴇғʀᴀᴄᴛɪᴏɴ ᴄᴏɴᴠᴇʀɢᴇ ᴀᴛ ᴀ ᴘᴏɪɴᴛ ʙᴇғᴏʀᴇ ᴀ ᴍɪʀʀᴏʀ ᴏʀ ʟᴇɴs. ᴡʜɪʟᴇ ᴠɪʀᴛᴜᴀʟ ɪᴍᴀɢᴇs ᴀʀᴇ ғᴏʀᴍᴇᴅ ᴡʜᴇɴ ᴛʜᴇ ʟɪɢʜᴛ ʀᴀʏs ᴅɪᴠᴇʀɢᴇ ᴀғᴛᴇʀ ʀᴇғʟᴇᴄᴛɪᴏɴ ᴏʀ ʀᴇғʀᴀᴄᴛɪᴏɴ. ʀᴇᴀʟ ɪᴍᴀɢᴇs ᴀᴘᴘᴇᴀʀ ᴏɴ ᴛʜᴇ sᴄʀᴇᴇɴ ᴀs ᴀɢᴀɪɴsᴛ ᴠɪʀᴛᴜᴀʟ ɪᴍᴀɢᴇs ɴᴇᴠᴇʀ ᴀᴘᴘᴇᴀʀ ᴏɴ ᴛʜᴇ sᴄʀᴇᴇɴ.
(ʙ)ʙᴀsɪᴄᴀʟʟʏ, ᴛʜᴇ ʀᴇғʟᴇᴄᴛɪɴɢ sᴜʀғᴀᴄᴇ ᴏғ ᴄᴏɴᴠᴇx ᴍɪʀʀᴏʀ ʙᴜʟɢᴇs ᴏᴜᴛsɪᴅᴇ ᴡʜɪʟᴇ ᴄᴏɴᴄᴀᴠᴇ ᴍɪʀʀᴏʀ's ʙᴜʟɢᴇs ɪɴᴡᴀʀᴅs. ᴛʜᴇ ᴍᴀᴊᴏʀ ᴅɪғғᴇʀᴇɴᴄᴇ ɪs ᴛʜᴇ ɪᴍᴀɢᴇ ᴛʜᴀᴛ ғᴏʀᴍs ɪɴ ᴛʜᴇsᴇ ᴛᴡᴏ ᴍɪʀʀᴏʀs. ɪɴ ᴏᴛʜᴇʀ ᴡᴏʀᴅs, ᴅɪᴍɪɴɪsʜᴇᴅ ɪᴍᴀɢᴇs ғᴏʀᴍ ɪɴ ᴄᴏɴᴠᴇx ᴍɪʀʀᴏʀs ᴡʜɪʟᴇ ᴇɴʟᴀʀɢᴇᴅ ɪᴍᴀɢᴇs ғᴏʀᴍ ɪɴ ᴄᴏɴᴄᴀᴠᴇ ᴍɪʀʀᴏʀs.
3. (ᴀ) ᴡᴇ sʜᴏᴜʟᴅ ᴜsᴇ ᴀ sᴍᴏᴏᴛʜ sᴜʀғᴀᴄᴇ ʟɪᴋᴇ ᴍɪʀʀᴏʀ . ᴀs ᴍɪʀʀᴏʀ sᴜʀғᴀᴄᴇ ɪs sᴍᴏᴏᴛʜ ᴛʜᴇʀᴇ ɪs ɴᴏ ʀᴏᴜɢʜɴᴇss ɪɴ ᴛʜᴇ sᴜʀғᴀᴄᴇ ᴀɴᴅ ᴛʜᴀɴ ʀᴇғʟᴇᴄᴛɪᴏɴ ʀᴀʏ ᴡɪʟʟ ʙᴇ ᴇǫᴜᴀʟ ᴛᴏ ɪɴᴄɪᴅᴇɴᴄᴇ ʀᴀʏ ᴀɴᴅ ʟɪɢʜᴛ ᴡɪʟʟ ᴛʀᴀᴠᴇʟs sᴛʀᴀɪɢʜᴛ.
(ʙ) ᴅɪsᴘᴇʀsɪᴏɴ ɪs ᴀ ᴍᴇᴛʜᴏᴅ ᴏғ sᴘʟɪᴛᴛɪɴɢ ᴜᴘ ᴡʜɪᴛᴇ ʟɪɢʜᴛ ɪɴᴛᴏ ɪᴛs ᴄᴏɴsᴛɪᴛᴜᴇɴᴛ ᴄᴏʟᴏᴜʀs.
4. (ᴀ) sᴇᴇ ᴛʜᴇ ᴀᴛᴛᴀᴄʜᴍᴇɴᴛ
(ʙ)ᴛʜᴇ ɪᴍᴀɢᴇ ғᴏʀᴍᴇᴅ ʙʏ ᴀ ᴘʟᴀɴᴇ ᴍɪʀʀᴏʀ ɪs ᴀʟᴡᴀʏs ᴠɪʀᴛᴜᴀʟ (ᴍᴇᴀɴɪɴɢ ᴛʜᴀᴛ ᴛʜᴇ ʟɪɢʜᴛ ʀᴀʏs ᴅᴏ ɴᴏᴛ ᴀᴄᴛᴜᴀʟʟʏ ᴄᴏᴍᴇ ғʀᴏᴍ ᴛʜᴇ ɪᴍᴀɢᴇ), ᴜᴘʀɪɢʜᴛ, ᴀɴᴅ ᴏғ ᴛʜᴇ sᴀᴍᴇ sʜᴀᴘᴇ ᴀɴᴅ sɪᴢᴇ ᴀs ᴛʜᴇ ᴏʙᴊᴇᴄᴛ ɪᴛ ɪs ʀᴇғʟᴇᴄᴛɪɴɢ. ᴀ ᴠɪʀᴛᴜᴀʟ ɪᴍᴀɢᴇ ɪs ᴀ ᴄᴏᴘʏ ᴏғ ᴀɴ ᴏʙᴊᴇᴄᴛ ғᴏʀᴍᴇᴅ ᴀᴛ ᴛʜᴇ ʟᴏᴄᴀᴛɪᴏɴ ғʀᴏᴍ ᴡʜɪᴄʜ ᴛʜᴇ ʟɪɢʜᴛ ʀᴀʏs ᴀᴘᴘᴇᴀʀ ᴛᴏ ᴄᴏᴍᴇ.
