Question

ᴀ ꜱʜᴇʟʟ ᴏꜰ ᴍᴀꜱꜱ 3 ᴋɢ ᴇxᴩʟᴏᴅᴇꜱ ɪɴᴛᴏ ᴛᴡᴏ ꜰʀᴀɢᴍᴇɴᴛꜱ 1ᴋɢ ᴀɴᴅ 2ᴋɢ ᴀᴛ ɪᴛꜱ ʜɪɢʜᴇꜱᴛ ᴩᴏɪɴᴛ ᴡʜᴇɴ ɪᴛ ɪꜱ ᴩʀᴏᴊᴇᴄᴛᴇᴅ ᴀᴛ ᴀɴ ᴀɴɢʟᴇ 30° ᴡɪᴛʜ ʜᴏʀɪᴢᴏɴᴛᴀʟ 1ᴋɢ ᴍᴀꜱꜱ ʀᴇᴛʀᴀᴄᴇꜱ ɪᴛꜱ ᴏʀɪɢɪɴᴀʟ ᴩᴀᴛʜ ᴡɪᴛʜ ᴀ ᴠᴇʟᴏᴄɪᴛy 10 ᴍ/ꜱ ꜰᴀʟʟꜱ ᴀᴛ ᴛʜᴇ ᴩᴏɪɴᴛ ᴏꜰ ᴩʀᴏᴊᴇᴄᴛɪᴏɴ. ᴠᴇʟᴏᴄɪᴛy ᴏꜰ 2ᴋɢ ᴍᴀꜱꜱ ᴀꜰᴛᴇʀ ᴇxᴩʟᴏꜱɪᴏɴ ɪꜱ

Answer 1

Explanation:

Solution - Firstly finding the power of combination of two lenses, which will be the algebraic sum of individual power.

Power = +6 + + (-2)

Power = 4D.

Power and focal length are inversely related with each other. Thus, focal length of combination will be -

f = 1/P

f = 1/4

f = 0.25 metre.

Hence, focal length of the combination is 0.25 metre.