Read the given passage and answer the questions that follow:

A global light pollution map developed by a group of researchers has ranked New Delhi, Kolkata and Bengaluru as the three cities with the highest light pollution in India. It should serve to alert us to the looming problem of light pollution about which we are not only doing so little to prevent but are also unaware about. Light pollution refers to the harmful impact of artificial outdoor lighting. While artificial outdoor lighting is needed in the form of street lights as it increases safety on roads and enables us to study and work in the dark, its use for floodlighting, illumination, advertising, etc. has grown manifold in recent decades, resulting in the problem of light pollution. Studies show that the brightness from outdoor lights has risen steadily across India over a 20 year period, with New Delhi, Telangana, Maharashtra, Karnataka and Uttar Pradesh showing a “very high light intensity pollution” rise between 1993 and 2013. The use of excessive artificial outdoor lighting has several harmful implications not just for human health but for the wellbeing of animals, birds, insects and our environment. Use of artificial lights at night gives us more working and studying hours but it results in the problem of ‘loss of night’. We find it difficult to fall asleep when the glow of streets enters our homes. It impacts our sleep-wake rhythm, which could have serious implications for our moods and health. Illumination of gardens impacts animals and insects too. It is nocturnal insects and birds that suffer the most due to light pollution. It makes them disoriented, impacts their reproduction and thus, their populations.

Light pollution intensity refers to: