an object 4.0 CM in size is placed at 25.0 CM in front of a concave mirror of focal length 15.0 CM. at what distance from the mirror should a screen we placed in order to obtain a sharp image ? find the nature and size of the image?
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an object 4.0 CM in size is placed at 25.0 CM in front of a concave mirror of focal length 15.0 CM. at what distance from the mirror should a screen we placed in order to obtain a sharp image ? find the nature and size of the image.
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ɢɪᴠᴇɴ
sɪᴢᴇ ᴏғ ᴏʙᴊᴇᴄᴛ , ʜ₀ = 4ᴄm
ᴏʙᴊᴇᴄᴛ ᴅɪsᴛᴀɴᴄᴇ , ᴜ = -25ᴄᴍ
ғᴏᴄᴀʟ ʟᴇɴɢᴛʜ ᴏғ ᴄᴏɴᴄᴀᴠᴇ ᴍɪʀʀᴏʀ , ғ = -15ᴄᴍ
ᴜsᴇ ғᴏʀᴍᴜʟᴀ ,
1/ᴠ + 1/ᴜ = 1/ғ
⇒1/ᴠ + 1/-25 = 1/-15
⇒1/ᴠ = 1/-15 + 1/25 = (-25 + 15)/375 = 1/-37.5 ᴄᴍ
⇒ ᴠ = - 37.5 ᴄᴍ ,
∴ ɪᴍᴀɢᴇ ɪs ғᴏʀᴍᴇᴅ ᴏʙᴊᴇᴄᴛ sɪᴅᴇ , 37.5ᴄᴍ ғʀᴏᴍ ᴘᴏʟᴇ ᴏғ ᴄᴏɴᴄᴀᴠᴇ ᴍɪʀʀᴏʀ.
ɴᴏᴡ, ᴜsᴇ ғᴏʀᴍᴜʟᴀ,
ʜɪ/ʜ₀ = -ᴜ/ᴠ
ᴡʜᴇʀᴇ ʜɪ ɪs ᴛʜᴇ sɪᴢᴇ ᴏғ ɪᴍᴀɢᴇ .
ɴᴏᴡ, ʜɪ/4ᴄᴍ = -(-37.5ᴄᴍ)/(-25ᴄᴍ)
ʜɪ = -4 × 37.5/25 ᴄᴍ = -6ᴄᴍ
∴ sɪᴢᴇ ᴏғ ɪᴍᴀɢᴇ = 6ᴄᴍ
ʜᴇɴᴄᴇ,sʀᴇᴇɴ sʜᴏᴜʟᴅ ᴘʟᴀᴄᴇ 37.5 ᴄᴍ ʟᴇғᴛ sɪᴅᴇ ᴏғ ᴍɪʀʀᴏʀ ᴀɴᴅ sɪᴢᴇ ᴏғ ɪᴍᴀɢᴇ ɪs 6ᴄᴍ .ɪᴛ ɪs ɪɴᴠᴇʀᴛᴇᴅ ᴀɴᴅ ʟᴀʀɢᴇʀ ᴛʜᴀɴ ᴏʙᴊᴇᴄᴛ's sɪᴢᴇ.