Question 1 (Total 20 marks) (X = 2 for odd no. in the last digit of student ID; X = 4 for zero or even no. in the last digit of student ID) Edan gives response to difference levels of light measured in luminances. He can detect light with the response "Y" and cannot detect light with the response "N". The results are shown in Table 1. He cannot detect a difference when the luminance varies by 1X% from a reference luminance above the threshold. Based on a perceived brightness of 10 units for a reference luminance of 500 ed/m', he perceives a luminance of 2X0 cd/m as 6 units and a luminance of 400 cd/m as 9 units. Weber's law is applicable for him to detect a difference in luminance and Stevens' power law is applicable for him to perceive brightness at different luminances. Luminance (cd/m2) 0.1 0.2 0.3 0.4 0.5 Test 1 N N N Y Y Test 2 N N Y Y Y Test 3 N N N Y Y Test 4 N N Y Y Y Table 1 Response to different luminances (a) Find the threshold luminance and state the method used based on results in Table 1. (b) Evaluate the range of luminances he can detect a difference from 4X0 cd/m. Hence discuss whether he can distinguish a luminance of 460 cd/m from the reference of 4X0 cd/m'. (c) Find a mathematical expression showing his perceived brightness "P" in terms of the luminance "S". Hence explain whether his perception is a case of response compression, linear response or response expansion