A student has difficulty in reading the blackboard while sitting in the last row. It shows that he is unable to see distant objects clearly. He is suffering from myopia. This defect can be corrected by using a concave lens.

Give reasons:
(i) The sky appears dark to passengers flying at very high altitudes.
At very high altitudes, passengers are above the atmosphere where there is less scattering of sunlight. As a result, they do not see the scattered blue light and the sky appears dark, similar to the condition experienced by astronauts in space.
(ii) 'Danger' signal lights are red in color.
सोलर पैनल वाली कंपनी 'उर्जा' की ओर से अपने उत्पाद की जानकारी देने और बिक्री बढ़ाने हेतु एक आकर्षक विज्ञापन तैयार कीजिए।