Question 2: Lens Property: A new plastic lens material "SR-47" is being proposed for release onto the market. The specif

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Question 2 Lens Property A New Plastic Lens Material Sr 47 Is Being Proposed For Release Onto The Market The Specif 1 (94.64 KiB) Viewed 11 times

Question 2 Lens Property A New Plastic Lens Material Sr 47 Is Being Proposed For Release Onto The Market The Specif 2 (94.64 KiB) Viewed 11 times

Question 2: Lens Property: A new plastic lens material "SR-47" is being proposed for release onto the market. The specification of the lens (in comparison to existing materials, Crown Glass, CR-39 and Polycarbonate) is shown below: . ● · Refractive Index Abbe Specific Gravity Transmittance Impact Resistance 13 You are to assess the suitability of this new lens for use as an ophthalmic lens in a 'dress frame' (ie. spectacles for everyday use). Summarise SR-47's relative advantages and disadvantages versus CR- 39 and how this will affect the lens property. State if you recommend or not recommend SR-47 for the stated purpose. ANSWER 2-1 Dot point as below encouraged (3 marks) Refractive Index: Abbe: Specific Gravity: ● Transmittance: ● Impact Resistance: ● Crown Glass 1.52 60 Recommendation: CR-39 1.49 58 2.54g/cm3 99% Low Polycarbonate 1.31g/cm3 99% Moderate 1.59 32 SR-47 1.67 32 1.20g/cm3 99% High 2.69g/cm3 147% High You are to design an anti-reflective coating for SR-47. Assuming a wavelength of 570nm is used as the reference wavelength, the coating should have the following characteristics. ● Refractive index: ANSWER 2-2 (to TWO decimal place, nark) Thickness: ANSWER 2-3 nm (1 mark)