shared via CourseHero com This study resource was This study source was downloaded by 100000828946667 from CourseHero com on 11 07 2021 13 49 29 GMT 06 00 https www coursehero com file 87584142 Activity 6 Light Intensity pdf Last Modified Oct 2020 by P M Ong For DLSU use only NOT FOR CITATION SALE NOR REDISTRIBUTION Page 1 of 10 EXPERIMENT NO 6 LIGHT INTENSITY OBJECTIVE To establish the relationship between light intensity and distance BACKGROUND In this activity we will observe how light intensity from a light source changes with distance Light intensity from a point source as expressed in unit lux is a measure of how much light falls on a certain area The effect of distance to light intensity is predicted to follow the inverse square law the light intensity cid 1 cid 2 decreases by a factor of four as the distance from the light source doubles and decreases by a factor of nine as the distance triples and so on This is clearly illustrated in Fig 1 1 Fig 1 Visual propagation of light following the inverse square law shared via CourseHero com This study resource was This study source was downloaded by 100000828946667 from CourseHero com on 11 07 2021 13 49 29 GMT 06 00 https www coursehero com file 87584142 Activity 6 Light Intensity pdf Last Modified Oct 2020 by P M Ong For DLSU use only NOT FOR CITATION SALE NOR REDISTRIBUTION Page 2 of 10 MATERIALS TOOLS Mobile phone with Google s Science Journal App Light source e g light bulb Do not use laser Measuring tape Room that can be darkened well enough and cleared of objects that can reflect light Adhesive tape optional to secure your measuring tape Phone holder optional for a stable measurement Nonreflective cover optional to cover reflective surfaces along the measurement path PROCEDURE Precautionary Measure If you are going to use a flashlight as your light source be sure not to directly put your phone within the hotspot of the beam of the flashlight If the beam is too concentrated hotspot you may need more distance for the inverse square to be applicable Preliminary Download the Google s Science Journal App on this link https www sciencebuddies org blog science journal app Familiarize yourself with the Google s Science Journal App and light sensor by viewing this link https www sciencebuddies org blog google science journal app tutorial part4 light sensor from Blog Snapshots of the parameters of brightness recording as viewed on iOS are shown in Figs 3 and 4 Note that the data of brightness is expressed in EV Exposure Value since an Apple smartphone uses the phone s camera to measure the brightness Similar parameters would be shown on Android except that the data is in lux since it utilizes the ambient light sensor in measuring light intensity Fig 2 Flashlight beam anatomy hotspot and spill 2 shared via CourseHero com This study resource was This study source was downloaded by 100000828946667 from CourseHero com on 11 07 2021 13 49 29 GMT 06 00 https www coursehero com file 87584142 Activity 6 Light Intensity pdf Last Modified Oct 2020 by P M Ong For DLSU use only NOT FOR CITATION SALE NOR REDISTRIBUTION Page 3 of 10 Fig 3 Google s Science Journal App iOS parameters of Recording screen and their description 2 Fig 4 Google s Science Journal App iOS parameters of Review screen and their description 2 shared via CourseHero com This study resource was This study source was downloaded by 100000828946667 from CourseHero com on 11 07 2021 13 49 29 GMT 06 00 https www coursehero com file 87584142 Activity 6 Light Intensity pdf Last Modified Oct 2020 by P M Ong For DLSU use only NOT FOR CITATION SALE NOR REDISTRIBUTION Page 4 of 10 1 Find a room where you can have the dimmest environment possible Since you are going to measure light intensity from a specific source any other source of light that is too close to your setup may influence your measurement Take note if the ambient light affects your measurement later 2 Set up the light source measuring tape and mobile phone like the sample setup presented in Fig 5 Some things to consider for your setup o Make sure that light sensor of your mobile phone is of the same height as the light source o Place the measuring tape so it will be easier for you to read the distance between the light source and the light sensor of your mobile phone o Configure your setup in such a way that it would be easier for you to glide your phone towards the light source Meaning you will start your measurement from a far distance and slowly moving towards the light source as you measure the changes in light intensity with distance Further instructions are in 5 o You may want to use a phone holder to minimize the influence of an angled sensor from the light source and to maximize stability of your setup During measurement your phone s screen should be positioned perpendicular to the light source as possible 3 Take a photo of your setup You may use some marker in place of your mobile phone so you can use your mobile phone s camera 4 Turn on your light source and darken the room o Minimize stray sources of light that are inside the field of view of your mobile phone s light sensor This can be reflective objects that could directly influence your measurement o Note that some light source e g light bulbs need a few minutes to reach their maximum brightness You could gauge the brightness stability of your light source Fig 5 Sample setup 3 shared via CourseHero com This study resource was This study source was downloaded by 100000828946667 from CourseHero com on 11 07 2021 13 49 29 GMT 06 00 https www coursehero com file 87584142 Activity 6 Light Intensity pdf Last Modified Oct 2020 by P M Ong For DLSU use only NOT FOR CITATION SALE NOR REDISTRIBUTION Page 5 of 10 by pointing your phone s light sensor to the light source at a distance and observing an unfluctuating data for a few seconds e g 10 s 5 Know and record 10 distances by identifying first the starting point The starting point is the farthest distance where any measurement is very low and changes minimally with gradually changing distance either increasing or decreasing distance The distance interval is set at 2 5 cm to optimize the data resolution While the final distance is the distance closest to the light source Meaning you are to start from the farthest distance possible and slowly glide your phone towards the light source The table in your data sheet for the distance covered is intentionally left blank so you can start to design your own experiment The