Question

I need help with question b)

Answer 1

Most were only slightly larger than modern dragonflies, but the group does include the largest known insects, such as the late Carboniferous Meganeura monyi, Megatypus, and the even larger later Permian Meganeuropsis permiana, with wingspans of

up to 71 cm (2 ft 4 in).

Ⓖ︎Ⓞ︎Ⓞ︎Ⓓ︎ Ⓜ︎Ⓞ︎Ⓡ︎Ⓝ︎Ⓘ︎Ⓝ︎Ⓖ︎ Ⓓ︎Ⓔ︎Ⓐ︎Ⓔ︎..❤️❤️

Answer 2

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Given:

• Distance of insect(u) = -4cm
• Focal length(f) = +6cm
• Height of insect(h1) = +0.5cm

To Find:

• Image location (distance of image from lens)(v)
• Height of image(h2)

Solution:

$\bf{1.\:\: Image\: location} \\\\\text{By Lens formula:} \\\\:\implies \dfrac{1}{v} - \dfrac{1}{u} = \dfrac{1}{f} \\\\:\implies \dfrac{1}{v} - \dfrac{1}{-4} = \dfrac{1}{6} \\\\:\implies \dfrac{1}{v} + \dfrac{1}{4} = \dfrac{1}{6} \\\\:\implies \dfrac{1}{v} = \dfrac{1}{6} - \dfrac{1}{4} \\\\:\implies \dfrac{1}{v} = \dfrac{2}{12} - \dfrac{3}{12} \\\\:\implies \dfrac{1}{v} = \dfrac{-1}{12} \\\\\bf{:\implies v = \dfrac{12}{-1} = -12cm}$

$\bf{2. \:\:Height \:of \:image} \\\\\text{By Magnification Formula:} \\\\:\implies m = \dfrac{v}{u} = \dfrac{h_2}{h_1} \\\\:\implies \dfrac{v}{u} = \dfrac{h_2}{h_1} \\\\:\implies \dfrac{-12}{-4} = \dfrac{h_2}{+0.5} \\\\:\implies 3 = 2h_2 \\\\\bf{:\implies h_2 = \dfrac{3}{2} cm = 1.5cm}$

Formulae used:

• Lens formula => 1/v - 1/u = 1/f
• Magnification formula => m = v/u = h2/h1

Learn More:

1. Mirror formula => 1/v + 1/u = 1/f

• Magnification formula => m = -v/u = h2/h1