reflection

1. noun The throwing back by a body or surface of light, heat, or sound without absorbing it.

example
In modern cities high-rise buildings are casting long shadows across neighbouring urban areas, making dense dark cities energetically inefficient and less sustainable. Hong Kong is the city with the highest concentration of skyscrapers in the world. At times, the reflection of light from surrounding buildings is the only natural light source available on the ground.

2. noun Serious thought or consideration.

example
Natural light is driving basic biological processes. Health effects of chronic low-exposure to direct natural light include vitamin D deficiency, short-sightedness and depression. A thoughtful reflection is needed to introduce new regulations in urban planning. Sufficient access to natural light is fundamental to improve public health, quality of life and sustainability in modern cities.