This research aims to determine the effect of smartphone-based learning media in the students' critical thinking skills. This research was a quasi-experimental with only Posttest Control Group Design. The sample of this reasearch were students of class XI MIPA 1 and XI MIPA 2 at SMAN 1 Ngaglik in the academic year 2019/2020 who were taken by simple random sampling. Data collection instrument was developed based on indicators critical thinking skills namely understanding, application, analysis, evaluation, and generalize. The analysis of this research used descriptive analysis and independent t test. The results of t test analysis showed critical thinking skills of experimental class were significantly higher than the control class. It means that the use of smartphone-based learning media has an effect in improving the critical thinking skills of students.

One of the learning media with mobile technology that can be used for education is 'smartphone.' This study developed a smartphone-based learning media capable of supporting physics learning on Microscope topics for XI grade high school students with a specialization in Mathematics and Natural Sciences (MIPA). This development product is in the form of teaching materials that can be accessed through an application on a smartphone. This learning media is validated by media experts and content experts. The development model used is modified Borg & Gall with seven stages, namely the preliminary research stage and information gathering, the planning stage, the preliminary product development stage, the design validation, the main product revision, the main field testing, and the operational product revision stage. The data obtained were analysed using equations and interpreted in the interpretation of the validation results assessment score. This development results reveal the validity value of smartphone-based learning media by content experts and media experts. The validity of media expert's states that it is valid for product development and the validity of material expert's states that the content developed in learning media is very valid. The accumulated student response to the application of smartphonebased learning media is very good.